Answer:
D. External sex organs form .
Step-by-step explanation:
There are three stages in fetal development that include germinal, embryonic, and fetal period.
Three months means, it will be the 12 week of the fetal development and called fetal period. At the end of this stage, baby's external genitalia or sex organs will start developing such as penis in male and vagina in female.
Hence, the correct option is D.