4.正方体ABCD−A1B1C1D1ABCD-A_{1}B_{1}C_{1}D_{1}ABCD−A1B1C1D1的棱长为1,EEE,FFF,GGG分别为BCBCBC,CC1CC_{1}CC1,BB1BB_{1}BB1的中点,则正确的是((( )))