从A、B、C、D四个选项中，选出可以填入空白处的最佳选项。
例：It is generally considered unwise to give a child he or she wants.
A．however B．whatever C．whichever D．whenever
答案是B。
21．The old lady was nervous, she wasn’t used to a stranger calling late at night.
A．or B．for C．so D．and
22．There a number of visitors from Australia during that week.
A．is B．are C．was D．were
23．It was Sunday in November and Peter went hunting in forest to the west of his house.
A．a, the B．the, a C．the, the
