虚拟语气主句中should能用于第三人称吗?

虚拟语气主句中should能用于第三人称吗?
--Do you think he would have given you a hand in your time of financial difficulty?
--He_____if he had known about it. We are very good friends.
选项中只有should have最接近呢, 但是我怎么有印象是第三人称的虚拟语气话只能用would呢.
请各位高人帮我确认一下,谢谢先!