-- What did the teacher say to you?
-- He asked me ______.
A:why I look unhappy then
B:when did I go home last night
C:how could I solve the problem
D:if I had got everything ready
第一次世界大战爆发前,意大利加入同盟国集团;而第一次世界大战爆发后,意大利加入到协约国集团一方作战。这反映的实质问题是( )