题干
She likes _____ and _____.
A：singing; dancing
B：sing; dance
C：sings; dance
答案(点此获取答案解析）
A
She likes _____ and _____.
A：singing; dancing
B：sing; dance
C：sings; dance
=（sinθ，1）， 
=（1，﹣cosθ），θ∈（0，π）