(-a)2+((-a)2)=-a-a=-2a.
( )的出现说明企业以生产者为重心转向以消费者为重心。
A.生产观念
B.产品观念
C.市场营销观念
D.全面营销观念
He was late for the meeting because the bus he took _____ halfway. [ ]
A. broke in
B. broke down
C. broke out
D. broke up