答案：He seemed to have regained his health after the operation.
解析：这里考察的是seem的两种常见用法,即
It seem that sb do 及 sb seem to do
后根据时态填have done那 He seemed to have regained his health after the operation。这句是非谓语嘛？to have regained 就是非谓语的部分啦 只是比较变形不好认 :)