All the people ________ at the party were his supporters．
A.presentB.thankfulC.interestedD.import在线课程A
解析：
题意为“所有出席宴会的人都是他的拥护者”。be present at“出席……”作定语时，省去“be present at”作了后置定语，be interested in“对……感兴趣的”，故只能选A。