A:for which
B:at which
C:with which
D:with which
①“枪杆子里出政权” ②“打倒列强,除军阀”
③“宁为战死鬼,不做亡国奴!” ④“外争国权,内惩国贼”
已知:如图所示,AB∥CD,BC∥DE.求证:∠B+∠D=180°
证明:∵AB∥CD
∴∠B=∠____ (____ )
∵BC∥DE,∴∠C+∠D=180°(____ )
∴∠B+∠D=180°(____ )