一年中四季变化比较明显的温度带是[ ]
A、热带
B、北温带
C、北寒带
D、南寒带
答案：B
The more one is _______ the English-speaking environment, the better he or she will learn the language.
A．filled in
B．exposed to
C．caught on
D．kept up
构造柱箍筋间距不宜大于（）mm。
A、250
B、300
C、400
D、500
