单项选择题 变压器运行时，其绕组和铁芯产生的损耗转变成（   ）， —部分被变压器各部件吸收使之温度升高，另一部分则散发到周围介质中。 A. 热量 B. 有功  C. 无功 D. 动能

未知题型 A school bus has 10 double seats in each of 2 rows. Two students can sit in each double seat. If an empty bus starts out and makes two stops, picking up three times the number of students at the second stop as at the first stop, and if the bus is then filled to seating capacity, how many students got on the bus at the second stop?E.30

判断题 一个机械结构只能建立一个装配尺寸链