题目

       After my 26 second-graders finished reciting the text, they settled back in their seats．But Duane was still __1__ there．Duane was a bright and lovable student, __2__ his mother, a single parent, had many problems such as drinking．__3__ that he might have had a bad night, I walked over to him to see what was wrong．As he looked up, I could see the __4__ in his dark eyes．        “Mrs. Brown, aren’t you going to open my present for you?” he asked __5__．“I put it on your desk．”        Getting back his gift from my desk, he handed it to me．I noticed椭圆（θ为参数）的离心率为（ ）A．B．C．D．