一般条件下，下列哪类冠桩固位最好

A．光滑柱形

B．槽柱形

C．铸造冠柱

D．螺纹状

E．弯制桩

根据括号内的要求改写下列句子，每空一词。

小题1:Study hard, or you’ll fail the exams. (改为同义句)

_________ you _________ study hard, you will fail the exams.

小题2:Mary is good at writing Chinese words. (改为同义句)

Mary _________ well _________ writing Chinese words.

小题3:“I can sing some English songs.” Li Ming said. (变为间接引语)

Li Ming said _________ _________ sing some English songs.

小题4: She went shopping last Sunday. (改为同义句)

She _________ _________ shopping last Sunday.

小题5:We will go somewhere to have a picnic. (改为否定句)

We _________ go _________ to have a picnic.