制备黑膏药最关键的步骤是（）
A.提取药物
B.炼油
C.下丹成膏
D.去火毒
E.摊涂
参考答案：B
Our class _______ 55 students at that time.
A．consisted of
B． consists of
C． made up of
D． was consisting of
假设戊股票现价为14元，则以该股票为标的的行权价格为15元的认购期权，其内在价值为（）
A.0
B.1
C.-1
D.-1
