题目:设函数f(x)在[a,b]上连续,在(a,b)内可导,且f′(x)>0,f(a)<0,f(b)>0,则根据零点定理,存在c∈(a,b)使得( )。A. f(c)=0B. f′(c)=0C. f(c)=f(a)D. f(c)=f(b)