选择正确的答案完成句子。

1. Are these your _______________ (suitcase / suitcases)?

2. These are our _______________ (toothbrushes / toothbrush).

3. Mother _______________ (washing / washes) dishes in the sink.

4. I'm _______________ (take / taking) a shower in the bathroom.

5. Jenny is _______________ (siting / sitting) on the couch.

中国封建社会末期，封建政府对外推行“海禁”与“闭关锁国”政策。下列关于明清海禁政策的表述，正确的是

①明初和清初实行海禁的直接原因相同   ②海禁是完全禁止对外贸易  

③海禁严格控制对外贸易               ④都根源于自给自足的自然经济

A．①③

B．①②

C．②③

D．③④