货币在执行价值尺度职能时是（ ）
A．价值不变的特殊商品
B．观念上的货币
C．现实的货币
D．一种价值符号
B
—What are you going to do this Sunday?
—John has planned a big party on Sunday and many friends _______ to take part in. [ ]
A. will invite
B. has invited
C. will be invited
D. has been invited
氨力农可（）。
A.促使钙进入细胞内
B.阻滞钙进入细胞内
C.促使钾进入细胞内
D.促使钾排出细胞外
E.阻断钠进入细胞内
