What do A, B, C and D represent in the following figure?

(1) A : carrier protein, B : symport, C : uniport, D : antiport

(2) A : carrier protein, B : uniport, C : antiport, D : symport

(3) A : carrier protein, B : antiport, C : symport, D : uniport

(4) A : carrier protein, B : uniport, C : symport, D : antiport

Substances that enter the living cells by facilitated diffusion are:

1. generally polar in nature

2. transported in the direction of the concentration gradient 

3. transported with the help of carrier proteins 

4. all of the above

Diffusion is very important to plants since:

1. The cells have a permeable cell wall

2. It is the only means for gaseous movement within the plant body.

3. Plants cannot transport material by active transport.

4. They are unable to move towards the source of the nutrients.

Main factor deciding rate of diffusion is :-

1. Pressure/concentration gradient

2. Solubility of gases

3. Thickness of diffusion membrane

4. Posture of body 

Rate of diffusion of substances is affected by all, except

1. Gradient of concentration

2. Temperature but not pressure

3. Density

4. Both temperature and pressure

Simple diffusion is not saturated because

1. There is no requirement of energy

2. There is no requirement of carrier protein

4. It occurs along the concentration gradient

4. More than one option is correct