The Americans _____ about five days to get to the moon in 1969.
A:takes
B:cost
C:took
D:take
鸟类的体表被覆____,前肢变成____,具有迅速飞翔的能力;身体内有____;体温高而____.鸟类的身体结构和生理特点是与它的____生活相适应的.