(Ⅰ)求函数f(x)的最小正周期和最小值;
(Ⅱ)在△ABC中,A,B,C的对边分别为a,b,c,已知c= 3 ,f(C)=0,sinB=2sinA,求a,b的值.
For our safety, we'd better avoid ____ (go) out alone at night.