A.-20″ B.+20″ C.+4″ D.-4″
A.后前前后、往返 B.往返、后前前后 C.后后前前、往返 D.兩次同向、后后前前
A.+31.401m,+66.420m B.+31.401m,66.420m C.-31.401m,+66.420m D.-66.420m,+31.401m