D 十分虚弱, very是程度副词,修饰weak
D three-feet deep 形容词作定语,修饰hole,three和feet中间要用连字符
A much修饰不可数名词room,程度副词too修饰much,表示太多
B It's necessary for sb(主格) to do sth或It's necessary+ that从句 表示做某事很有必要
him是主格he的宾格
D such 修饰名词 ;too`````too
D a/an +可数名词;两个名词用连字符链接修饰名词相当于形容词
A much修饰不可数名词,too much+n 固定搭配
B It's necessary that....../It's necessary for sb.to do sth. 因为句子是强调立即还书的必要性是一件事,所以用从句。