Whales and dolphins have been found with hind limbs; this rareoccurrence is due to the reemergence of a trait they inherited from their terrestrial ancestors.
发现鲸和海豚身上有后肢;这种稀有的现象是由于它们在陆地上的祖先身上的特征再次被遗传。
3
This is rareoccurrence as our climate seldom goes to extremes.