The correct answer to this question is A, To gather light. Leaves on plants have a number of purposes, which vary by their size and shape. Plant leaves are important for a variety of different reasons. One is that they take in the Sun's energy.
The energy that is taken in is then used and converted into food. This is how plants grow. Larger plants take in light. This would be seen in a rainforest setting, that is crowded with other plants. On the other hand, plants that are around a lot of wind need plants that are smaller and strong so that they can survive.