He must have been here yesterday,( 改为反义疑问句

He must have been here yesterday,( )? 改为反义疑问句
He must have been here yesterday, didn't he?
因为 must +完成形式have been here yesterday表推测,意思是：“你昨天一定来过这里”.又因为是时间是【昨天】,是过去时,所以反义疑问部分,应该是didn't he?可是答案是wasn't he不好意思。He must have been here yesterday, wasn'the?因为 must +完成形式have been here yesterday表推测，意思是：“你昨天一定来过这里”。又因为是时间是【昨天】，是过去时，谓语动词是be，所以反义疑问部分要用be的过去形式，应该是wasn't he?