在机械制图中，物体的正面投影称为( )。
A．主视图
B．俯视图
C．左视图
D．右视图
参考答案：A
噬菌体、大肠杆菌、水稻和青蛙等生物体结构或细胞中都具有的糖是[ ]
A．脱氧核糖
B．纤维素
C．肌糖原
D．乳糖
—An ant has two stomachs—one for itself, one for others.
—Really? Quite interesting. I ________ anything about it.
A．don't know
B．have known
C．haven't known
D．didn't know
