高效液相色谱法测定固定污染源中苯并［a］芘时，实验室所用的玻璃仪器必须用（）浸泡洗涤。
A．环己烷
B．洗洁净
C．巳重铬酸钾
参考答案：C
No one would have time to read or listen to an account of everything ______ going on in the world.
A．it is
B．as is
C．there is
D．what is
电流继电器线圈的特点是线圈匝数少，导线粗，阻抗小，只有这样线圈（）才小。
