烟株缺铜的典型症状是（）
A、表现永久性萎焉
B、叶片组织坏死
C、生长缓慢
D、出现叶斑
参考答案：A
I suggest that that we should take part in more such activities in future ________we did yesterday.
A．which
B．as
C．that
D．than
下列物质中，属于高分子化合物的是[ ]
A.油脂
B.蔗糖
C.羊毛
D.高级脂肪酸
