设函数ƒ(x)在[a，b]上连续且ƒ(x)>0，则（ ）
A <img src="https://www.beizhujiaoyu.com/uploads/202208/20191017114717_4305.png" width="86" height="27" /> B <img src="https://www.beizhujiaoyu.com/uploads/202208/20191017114721_0242.png" width="86" height="27" /> C <img src="https://www.beizhujiaoyu.com/uploads/202208/20191017114724_2899.png" width="86" height="27" /> D <img src="https://www.beizhujiaoyu.com/uploads/202208/20191017114728_0555.png" width="159" height="27" />
（ ） 
