种子包衣和消毒是预防和减轻作物病害的有效措施之—（）
A.正确
B.错误
C.不恰当
参考答案：A
. If it _____ sunny, we _______ a picnic. But it is raining now.
A．had been, could have had
B．were, could have
C．had been, had
D．is, could have
大洋洲面积是南美洲的（）。
A．50％
B．70％
C．60％
D．无法确定
