手中握着一个圆柱形玻璃杯在空中静止，如图所示，杯和牛奶总重2N，则手对杯子的摩擦力__________
2N(填“小于”、“大于”或“等于”)。
等于
—Could you tell me ________?
—Ｏf course, last night.
A．how you came to our school.
B．when you reached our school.
C．when you reach our school.
D．when did you reach our school.
Coombs试验是一种（）
A.沉淀试验
B.中和试验
C.电泳试验
D.ELISA
E.凝集试验
