The retiring teacher made a speech ___ he thanked the class for the gift.
(A)which
(B)in which
(C)that
(D)to which
答案为(B)
不是以后面的 thank to 然后往前丢吗？
问别人却说是 made a speech in
但这样就不符合文法了吧...求解！

这题答案有错，(B) in which 才对句子还原: The retiring teacher made a speech.She thanked the class for the gift in the speech.