根据句意及首字母提示完成单词。

1. After dinner, Lisa usually helps her mother do the d       .

2. Linda likes to do housework.  She often helps her mom to s        the floor.

3. Mrs Wang h       watching TV, but she likes reading.

4. Brad didn't take part in the sports m        because of his sore back.

S=(D₁-D₂)/H=K/H中关于H的叙述，错误的是

A．指照片上两相邻组织影像密度界限的清楚程度
B．称为模糊值
C．亦称不锐利度
D．或称密度移行距离
E．以mm为单位