从构造上讲，大放脚底面至防潮层为基础墙。( )
参考答案：错
下列物质的主要成分是糖类的是（ ）
A．大米
B．鸡蛋
C．牛奶
D．花生油
The toughest thing about success is ________ you have to keep on being a success.
A．why
B．when
C．what
D．that
