题目

They usually have _____ to do after school.A. lots of homeworks             B. lots of homeworkC. a lot of homeworks             D. lot of homework 答案：B    第一个发现电流磁场的科学家是________；第一个发现电磁感应现象的科学家是________；第一个给出电荷间力的定量关系的科学家是________。