Hand cream is made mostly from oil based products. Stomata, small gaps in the leaves, arr mostly located on the under surface of the leaf. Little or no stomata are present at the top surface. Stomata are needed to allow gases to enter and exit the leaf. For photosynthesis, carbon dioxide needs to enter the leaf through the stomata. Hand cream covers the stomata for leaf B, preventing gases from entering or leaving. Hence, photosynthesis cannot occur, so the leaf is unable to make food and will eventually die off. (Yellowing is the start of this).