设集合Z₂₆=0，1，…，25)，乘法密码的加密函数为E_k:Z₂₆→Z₂₆，Ek(i)=(ki) mod 26，密钥k∈Z₂₆-0，则加密函数E₇(i)=(7i)mod 26是一个（）函数。

A．单射但非满射

B．满射但非单射

C．非单射且非满射

D．双射

_____he had not hurt his leg, John would have won the race.

A．If

B．Since

C．Though

D．When