Many of the at-risk behaviors of HIV and AIDS are actually related to cultural beliefs and （），while shaping by an array of complex social，economic，and political factors.

A.A party is where you go to have a good time.
B.Democracy is a system of government in which every citizen in the country can vote to elect its government officials.
C.An astronomer is one who studies astronomy.
D.Pollution is the process that chemicals are dumped into rivers.

A.catch
B.to catch
C.catching
D.caught