Testosterone stimulates the reproductive organs to develop into male organs.
For men, however, the hormone in question is testosterone.
A hormone stimulates the reproductive organs to develop into male organs.
What stimulates the reproductive organs to develop into male organs?

[1] a hormone
[2] bioaerosols
[3] Energy.
[4] Energy
[5] Leptospirosis
[6] a doorbell
[7] seeds
[8] Chlorophyll