Hello. I am Amy. I am eight years old. Today is my birthday. Look, I have a birthday cake. I have juice and rice for dinner. And I have many gifts, too. A red toy monkey, two new bags and five storybooks. I am so happy today.

如图，在直角梯形ABCD中，AD∥BC，∠A=90°，AB=BC=4，DE⊥BC于点E，且E是BC中点；动点P从点E出发沿路径ED→DA→AB以每秒1个单位长度的速度向终点B运动；设点P的运动时间为t秒，△PBC的面积为S，则下列能反映S与t的函数关系的图象是(  )