可调式减压阀宜()安装。
A.水平
B.竖直
C.倾斜
D.视情况而定
参考答案：A
—What do you think of the cook?
—He cuts the meat of all.
A.very finly B.more finely C.the most finely
DNA在下列哪一个温度下会变性？[ ]
A．20℃
B．40℃
C．60℃
D．100℃
