完形填空：阅读下面短文，从短文后各题所给的四个选项(A、B、C和D)中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
The dolphin (海豚) swam in her tiny tank. It was early evening and the park was 1. She was alone again.
Earlier that day, she had performed her 2 for the visitors; and though their cheers pleased her, they did not 3 the sadness of forced separation (分离) she experienced daily, 4 her family.
Later that afternoon, her keepers had done their usual set of 5 on her to make sure she would be ready for the next day's show. This time, she had given in quietly to their attentions. This 6 them, as it always did; they were so happy when she 7 them. But, when she didn't, they thought there was a 8; and she would be punished.
She dived down and stared through the glass window into the observatory (观察) room. During the day, 9 crowded into this viewing room to watch her from an underwater angle (角度). The glass was 10 with the hand prints of the children who had pressed 11 to get a good 12.
Her daily life seldom 13. Trainers would teach her 14 tricks, to be added to her show. Sometimes, humans would bring their ill or 15 children to swim with her. And, over time, she would heal (治愈) them. But she'd always 16 the process (过程) so as not to expose her amazing ability to the humans.
She swam up to the 17; then stared 18 at the stars above.
She was far from her family; and she was 19.
In the dark she sang.
But none of her kind 20 her.
