Answer: C) Second trimester—bone starts to replace cartilage; fetus begins to produce urine
Step-by-step explanation:
The second trimester of pregnancy is months four, five, and six. The fetus's tissues become more specialized and begin to function. The heart is large enough for heartbeats to be heard with a stethoscope, bone replaces cartilage to form the early skeleton, and the mother begins to feel the fetus moving. The fetus also begins to form urine and discharge it into the amniotic fluid. In females, ovarian follicles begin forming, while the prostate gland develops in males.