关于声现象，下列说法中正确的是 （ ）
改革开放以来，为早日实现中华民族复兴的伟大梦想，在***的正确领导下，经过全国各族人民的不懈努力，取得了辉煌的成就。请结合所学知识回答下列问题：
—What did you do yesterday?—My brother took two friends of ________ to play chess with us. But I don't know _______ of them.
