Each number of corolla is called
none of these
The correct option is D.
Explanation for the correct option
Explanation for incorrect options
Option A
Sepal is the member of the first whorl of the flower called the calyx.
Option B
Stamen is the male reproductive structure that is part of the androecium.
Option C
The anther is a sac-like structure that contains pollen grains. It is a part of the stamen.
Petal is a member of the corolla.