If Lili attends a class reunion, then Xiaoqiang, Dazhuang and Li Tie will also join the class reunion. If the above conclusion is true, which of the following must also be true? ['if Lili does not attend classmates, then Xiaoqiang does not.', 'if Xiao Zhang, Da Zhuang and Li Tie are attending a class reunion together, then Lili also participates.', "if Lili and Xiaoqiang attend classmates' gathering, then Dazhuang and Li Tie will not attend.", 'if Li Tie does not attend classmates, then Lili does not attend.']