Jack, ______ his father ______ climbing the hill.
A:and; is
B:with; are
C:with; is
D:/; are
下面是3个氨基酸的结构式,由这3个氨基酸按顺序脱水缩合所形成的化合物中,含有的氨基、羧基和肽键的数目依次是
We don't think it's good to stay_____ late to play computer games.