刀具起点在（0，0)，从法向切入到(-20，0)点，铣CMOmm整圆工件，并法向切出，然后到达(-40，0)点。根据示图中的刀具轨迹判断，正确的程序是 。 "
A.…,N010 Gg0 G00 X-40.0 YO, N020 G01 X一20.0 YO F200.0, N030 G02 x_20.0 YO 120 0 jo, N040 G01 X-40.0 YO：
B.…,N010 G90 G00 X-40.0 YO,N020 G9lG01 G4lx-20.0 YO D01 F200.0,N030 G02 x_20.0 YO 120.0 jo,N040 G01 X-40.0 YO：
C.… N010 GgO G00 X-40.0 YO, N020 G01 G41 X20.0 YO D01 F200.0,N030 G02 X-20.0 YO I一20.0 jo, N040 G01 x-40.0 YO,
D.…NO10 Ggo G00 X-40.0 YO,N020 GOI G41 X-20.0 YO D01 F200.0,N030 G02)，__20.O YO 120.0 jo,N040 C01 G40 X-40.0 Y0, "
正确答案是D