Question Discussion & Solution

The correct answer is Concave.

• Myopia: A person suffering from myopia can see the near objects clearly while far objects are not clear.
  • A Concave lens (diverging lens) is used by people suffering from myopia.

Additional Information

• Hypermetropia: A person suffering from hypermetropia can see distant objects clearly but not near objects.
  • People suffering from hypermetropia uses a Convex lens.
• Astigmatism: This defect arises due to the difference in the radius of curvature of the cornea in the different planes
  • The cylindrical lens is used by people suffering from Astigmatism.

Concept:

Meaning of i++:

First, we read the i than after reading the value of i we are going to increment i this is nothing but post-increment.

Meaning of ++i: 

First, we increment i than we read the value of I, this is nothing but pre-increment:

Examine code:

int main( )
{
int i = 10;
int C = i++;   // assign i to C therefore C = 10 after assigning increment i by 1
printf("i = %d, C =  %d", i, C);
return 0;
}

Output:

i = 11, C =  10

Therefore value of i to be assigned to C, and then I to be incremented by 1

Table and chair both are made of wood

Similarly, shoes and belt both are made of Leather.

The correct answer is Element.

Key Points

• An electric room heater or an electric heater used for cooking contains a coil of wire.
• The coil of wire used in electric heaters is called a heating element.
• The heating coil of the electric room heater transfers the electric energy into heat energy.
• The elements become red hot and give out heat after connecting to the electric supply.
• The amount of heat produced in a wire depends on its material used, length, and thickness.
• The coil of the electric heater is made up of nichrome.
• Nichrome consists of 80% nickel, 20% chromium.

Additional Information

• The filament is usually made of very thin tungsten wire.
  • In an incandescent bulb, an electric current is passed through a metal filament.
• A cell is a single unit device that converts chemical energy into electric energy.
  • It produces electricity capable to run smaller appliances.
• A battery usually consists of a group of cells.

Mistake Points

• A filament is a fine resistance wire the purpose of which is to emit white light. 
• An element is a resistive wire the sole purpose of which is to produce heat.

The correct answer is Potato.

Modifications of Root

1. For storage of food
   • Roots are modified in some plants for storing reserve food materials.
   • These modified roots usually are swollen and assume different forms such as spindle-shaped, e.g., radish; top-shaped, e.g., beet, turnip; cone-like, e.g., carrot; indefinite shape, e.g., sweet potatoes.
   • Dahlia, Asparagus, Portulaca are some other examples of plants with modified roots for food storage.
2. Nodulated roots
   • The roots of pea and other leguminous plants have numerous swollen nodules on fine branches of roots.
   • These nodules are formed due to the symbiotic association of Rhizobium (bacterium) that live inside the root cortical cells of the roots.
   • They fix nitrogen and an active nodule is pink in colour.
3. For mechanical support
   • Roots are modified to provide mechanical support as seen in a banyan tree which has roots growing vertically/obliquely downwards (prop roots); sugarcane/maize in which roots arise from the nodes in the cluster at the base of the stem (stilt roots) and betel/black pepper in which nodes and internodes bear roots which help in climbing.
4. For gaseous exchange
   • Pneumatophores or breathing roots are found in plants growing in mangroves or swamps with saline water for exchange of gases.
   • They are erect peg-like structures with numerous pores through which air circulates e.g., Rhizophora mangle.

• Modifications of Stem

1. For storage of food
   • Stems get modified into underground structures for storage of food as seen in potato (tuber), ginger (rhizome), garlic (bulb), yam (corm).
   • Presence of an eye (node) in potato, distinct nodes with internodes and scaly leaves in ginger/yam, a cluster of roots at the base of the reduced stem in garlic/ onion, all indicate that these underground plant parts are modified stem.
2. For vegetative propagation
   • Plants besides reproducing sexually also propagate through vegetative parts.
   • For this purpose, stems may be modified into a runner (Cyanodon dactylon, Oxalis). Runners are slender prostrate branches arising from axillary buds;
   • stolon (e.g., mint, strawberry) which is a slender lateral branch arising from the base of the stem grows upward and then down to develop new daughter plants;
   • offset having a single long horizontal internode growing up to some distance and producing a tuft of leaves above and a cluster of roots below at the apex (Eichornia, Pistia) and
   • sucker, which arises from the underground part of the stem, grow obliquely and gives rise to a new shoot. (Chrysanthemum, Banana, Pineapple).
3. For protection
   • Some modified stem provides protection as thorns which are hard, pointed structures each representing a branch that arises from the axil of a leaf.
   • Thorns are found in plants like Duranta, Pomegranate, Acacia, Ber, Prosopis, Bougainvillea, Citrus, etc.
4. For support
   • Tendrils are modifications of the stem to provide support to plants, e.g., Vitis, passionflower, Bignonia etc.
5. For photosynthesis
   • Stems are also modified into Phylloclade, to facilitate photosynthesis.
   • Phylloclades are flattened/cylindrical stem or branches of unlimited growth (Cactus).