()主要用来提高强度,但含量过高时不利于焊接性。
A.碳
B.硅
C.硫
D.磷
参考答案:B
—Excuse me,Miss Smith. Could you tell me how to improve my spoken English?
—OK. The best way is to practice *
A.as soon as possible
B.as quickly as possible
C.as much as possible
D.as clear as possible
数据库管理系统中的数据操纵语言(DML)所实现的操作一般包括( )。
A.查询,插入,修改,删除
B.排序,授权,删除
C.建立,插入,修改,排序
D.建立,授权,修改