题干
He is sad because he doesn't know which d____ his company will take in the future.
答案(点此获取答案解析）
direction
=2i+j， 
=3i+kj，若A，O，B三点不共线，且△AOB有一个内角为直角，则实数k的所有可能取值的个数是（ ）
