A-A+
Why can the hummingbird hover and even fly bac
问题详情
Why can the hummingbird hover and even fly backwards？
A．Because its wings are large enough.
B．Because it can tilt its body.
C．Because it has whirling and horizontal blades like a helicopter.
D．Because it can produce down-draft of air by beating their wings very fast.此题为多项选择题。请帮忙给出正确答案和分析，谢谢！
参考答案
正确答案：D
解析：题目问：为什么蜂鸟可以盘旋飞行甚至可以倒退?“Hummingbirds have paralleled even this．They tilt their bodies so that they are almost upright and then beat their wings as fast as 80 times a second producing a similar downdraft of air．So the hummingbird can hover and even fly backwards．”通过这句话可知，蜂鸟震动翅膀的次数可以达到80次/秒，这样就可以产生一股类似下降的气流，所以，蜂鸟可以盘旋飞行甚至可以倒退。据此判断，应选择D。
