Answer:
The correct answer would be - low level of testosterone hormone.
Explanation:
Gynecomastia is a condition occurs in the male in which the male breast tissue swells which are caused by the reduced or low level of the testosterone or increased level of male estrogen hormone in males.
The proper balance of these two hormones namely male hormone testosterone and female hormone. The imbalance of these hormones causes gynecomastia condition.
Thus, the correct answer would be - low level of testosterone hormone.