Palaeopneustidae
古吸海膽科
??? 情景例句
I've got to explain about it.
我得解釋一下此事。
Three times a week I have to walk all the way to the gym for my Phys Ed class.
一周有三次，我為了參加體育課而必須走路到體育館。
And why only snakes? Cats, for instance, would be greatly helped; no running fights with large, fierce rats or tussles with grown rabbits -- just a bite and no more effort needed.
為什么只有蛇才有毒液呢？譬如說，如果貓有毒液，那對貓會大有幫助，它就不必再和又大又兇的老鼠邊跑邊博斗了，也不必再和大兔子扭斗了，只要咬一口，就不必再費大力氣。