To solve this problem, we need to identify the plant parts that consist of two generations, one within the other. Let's analyze each option:$\newline \bullet$(a) Pollen grains inside the anther:$\newline$ - Pollen grains represent the male gametophyte generation.$\newline$ - They develop within the anther, which is part of the sporophyte generation.$\newline$ - Therefore, this option consists of two generations, one within the other.$\newline \bullet$(b) Germinated pollen grain with two male gametes:$\newline$