Once the economic and social usefulness of the motor car was demonstrated and with its superiority to the horse being proved,much of the early hostility to it in rural regions disappeared.
b.and its superiority over the horse had been
c.and its superiority to the horse
我选c.因为根据并列原则,b项的had been是过去完成时
与前半句的时态不同,因为我认为是错误的
但答案选b,它说c项and 连接once 从句和名词短语its superiority,两者形式不对称.这是为什么?我认为 and its superiority to the horse(was)proved应该是因并列而省略吧