First, as the process is from left to right, we are in the presence of the formation of a vesicle. Then, we are sure this is endocytosis.
Endocytosis can serve different purposes, including uptake of nutrients (better call pinocytosis) and signal transduction. The last usually involves a receptor in the membrane that is attached by a particular signal molecule. In this image, there is no molecule binding a receptor. Moreover, we can observe several molecules (these are nutrients) being transported into the cell.
The answer is A. Endocytosis, uptake of nutrients.