题干
They arrived _________ Shanghai ________ a cold morning.
A：in, in
B：in, on
C：at, on
D：at, in
答案(点此获取答案解析）
B
They arrived _________ Shanghai ________ a cold morning.
A：in, in
B：in, on
C：at, on
D：at, in
的中心为原点，
是
与
,则