题干
Rescuers had to __________ the search because of worsening weather condition.
A：take off
B：call off
C：cut off
D：show off
答案(点此获取答案解析）
B
，∠BAC＝45°，∠BAC的平分线交BC于点D，M、N分别是AD和AB上的动点，则BM＋MN的最小值是（ ）． 
