Many elephants are poached. Their tusks are used to make valuable ivory objects.

A. As many elephants are poached, their tusks are used to make valuable ivory objects.

B. Unless many elephants are poached, their tusks are used to make valuable ivory objects.

C. Many elephants are poached because their tusks are used to make valuable ivory objects.

D. Many elephants are poached, so their tusks are used to make valuable ivory objects.