蛋白质的特性是 [ ]
A．遇吲哚酚试剂褪色
B．遇双缩脲试剂呈紫色
C．遇吲哚酚试剂变蓝色
D．遇双缩脲试剂褪色
答案：B
.
The teaching building is _________ by many trees, some ______ over 30 metres.
A．surrounded, measuring
B．surrounded, measured
C．surrounding, measured
D．surrounded, measure
在SQL分组与计算查询中，利用______短语可以对分组条件进一步加以限定。
