下列情况较不易发生继发龋的是（）

A.保留部分软龋间接盖髓充填

B.邻面洞的边缘伸展至颊舌轴角处

C.邻面洞的侧壁保留有无基釉

D.银汞充填洞形时洞缘角大于90°

E.窝洞充填时，磷酸锌粘固粉垫底材料覆盖轴壁和龈壁

句型转换。

1. Justin wants to buy 2 kilos of beef. (对划线部分提问) 

   How _______ beef ______ Justin want to buy?

2. It's necessary for you to study hard in the school. (同义句)

   _______ _______ study hard in the school.

3. The music is very nice. (改为感叹句)

   _______ _______ music it is!

4. Are these shoes Kitty's? (改为同义句)

   _______ these shoes ______ to Kitty?

5. Did he go to the cinema yesterday? (用next week改写)

   _______ he _______ to the cinema next week?