如果向南走20米记为是-20米，那么向北走70米记为是（ ），-50米表示（ ）。
70米、向南走50米
—He is tired now. He _____ stay at home and have a rest.
—Thanks, doctor. [ ]
A. has to
B. mays
C. need
D. can't
电磁结构
