—Hi, Susan, you look tired.

—I ______ for months for the coming celebration for the school’s 60th anniversary.

A．was preparing

B．have been preparing

C．had prepared

D．prepare

木通的入药部位是（）

A.藤茎

B.茎髓

C.含有树脂的木材

D.树干和根的心材

E.茎枝