请在表格中注明您的性别。

Please indicate your ___sex on the form.

医生建议年轻人在发生性行为之前要了解相关健康知识。

Doctors advise young people to learn about health before having ___sex.

兽医需要确定新生小狗的性别。

The vet needs to ___determine the sex of the newborn puppies.