Complementary nature of structure and function.
<span>ileocecal valve or sphincter</span>

Pollen grain is odd one among all the other three. Pollen grain in a male gametophytic structure. Whereas all the other three are found inside ovule (nucellus, micropyle and embryo sac).
Hope Helps:)
Acid rain can cause many problems, such as stripping paint and burning skin, but I believe the answer you are looking for is "decay," which is the process that occurs when an organism decomposes.
Answer:
Due to less number of chlorophyll.
Explanation:
The variegated leaves accumulates or produces less amount of food than non-variegated leaves under similar condition because variegated leaves has number of chlorophyll as compared to non-variegated leaves. Chlorophyll is a green pigment that is responsible for the photosynthesis in plants, without chlorophyll no photosynthesis occurs in the plants. The variegated leaves has less number of chlorophyll as compared to non-variegated leaves which leads to less production of food in variegated leaves.