_________ the exact departure time, he missed his train.

A．Not be told

B．Having not been told

C．Not having told

D．Not having been told.

下列关于酶的论述错误的是（）

A.有些酶是核酸

B.在0℃～37℃范围内，唾液淀粉酶的活性会随着温度的升高而提高

C.酶的数量因参与化学反应而减少

D.任何活细胞内都有酶的存在