执行全井坐岗。进入油气层前50米开始每（）分钟测量一次钻井液增减量。
A.10
B.15
C.20
D.25
参考答案：B
按要求句型转换。
1. They give us some candies as a treat. (改为同义句)
They give us a _______ _______some candies.
2. He does some homework at night.(改为否定句)
He _______do_______homework at night.
3. My father is a teacher .My mother is a teacher,too.(改为同义句)
My _______are_______teachers.
4. Amy goes to the school library every Wednesday.(对划线部分提问)
_______ _______does Amy go to the school library?
5. I help him, he helps me.(改为同义句)
We help _______ _______.
证券公司定向发行债券的担保金额原则上不少于债券本息总额的( )。
A．20% B．30% C．50% D．80%
