釉面砖和外墙砖一般采用（）砂浆粘贴.
A.1：3
B.2：5
C.1：2
D.1：1
参考答案：C
同号两数相乘，符号不变。[ ]
Our teacher told us last night that ___.
A．English is difficult to be learnt
B．the English is difficult to learn
C．the English language is difficult to learn
D．English language is difficult to learn
