1. (2019·江苏) 请认真阅读下面短文，从短文后各题所给的A、B、C、D四个选项中，选出最佳选项。

    Wildlife has been greatly threatened in the modem age. There are species (物种) that are 1 every day. The white-naped crane is a typical example. So scientists are trying their best to 2 the species from going out of existence.

    Chris and Tim work at a zoo, helping endangered cranes with their 3. Emma, a female crane, has been in their 4 since she arrived in 2004.

    Born at an international crane foundation, Emma was 5 by human caretakers. This led to an unexpected 6, though she had a wonderful time there. Emma had 7 taken herself as a crane and become deeply attached to humans. She 8 to live with male cranes, and even had a 9 for killing some of them, which made it 10 for her to become a mother.

    11, the two zookeepers didn't want to see the extinction (灭绝) of this precious species. With their patience and efforts, they successfully developed a 12 of artificial breeding (人工繁殖) and natural reproduction. This 13 Emma to give birth to five baby cranes.

    The two keepers are proud of their productive work. But before they can be 14, more efforts must be made, because the population of the crane in the wild is on the 15, and many other species appear headed toward extinction. 16, not everyone has realized that wildlife has thoughts, feelings, and most importantly, equal rights to survive.

    How can we 17 the ever-widening gap that separates us from other animals? Chris and Tim offered us the 18: human beings took it for granted that their 19 held all the solutions, but maybe their hearts can be a better 20.