4. 如图所示,在正方体ABCD−A1B1C1D1ABCD-A_{1}B_{1}C_{1}D_{1}ABCD−A1B1C1D1中,EEE为线段A1C1A_{1}C_{1}A1C1上的动点,则下列直线中与直线CECECE夹角为定值的直线为((( )))