下列各组数中，相等的一组是（　　）

A．（-3）³与-3³

B．（-3）²与-3²

C．4³与3⁴

D．-3²和-3+（-3）

_____ she had not spelt the word wrong, Cathy would have got a full mark.

A．If

B．Since

C．Though

D．When