During DNA Synthesis,how Is the 5' -OH of Deoxyribose Protected

During DNA synthesis,how is the 5' -OH of deoxyribose protected?

A) With a p-dimethoxytrityl group
B) With a benzoyl group
C) With an isobutryl group
D) With a β-cyanoethyl group
E) This group does not need to be protected.