Name at least 3 uses for the sun's energy.

The sun is very important for many reasons. For example, the sun is needed for plant photosynthesis and growing crops. It is also needed for human warmth. Animals survive by eating plants, and so do humans, so without plants then animals wouldn't have the nutrients and they would die, and so would humans.

1- photosynthesis
2- light energy for earth so it is cause of day and night
3-we need solar energy to get vitamin d which is very essential for bones

option a is correct i.e.

only sodium ions can pass through the membrane.

explanation:

in context to the membrane of nerve impulse, the outer membrane of neuron is semi permeable that is only sodium ions can pass through the membrane i.e. smaller ions can pass through the membrane while larger ions cannot pass through it.

The answer is observations and interpreting.