20.如图,在棱长为2的正方体ABCD−A1B1C1D1ABCD-A_{1}B_{1}C_{1}D_{1}ABCD−A1B1C1D1中,点EEE,FFF,GGG分别为A1B1A_{1}B_{1}A1B1,B1C1B_{1}C_{1}B1C1,B1BB_{1}BB1B的中点,若点PPP在线段EFEFEF上运动,则下列结论正确的为((( )))