It has a spring in it.
注：spring既有“發(fā)條”的意思，也有“泉”的意思。
更多英語(yǔ)謎語(yǔ)
What crime is punishable when attempted but not when committed?
What can you hold in your left hand but not in your right hand?
Foward I am heavy, but backward I am not. What am I?
What rock is also a food?