一段美满的恋情需要彼此关心并体恤对方的情感。A good relationship involves concern and sensitivity for each other's feelings.通常，只有在母亲面前他的情感才会如此外露。Normally, such an outward display of affection is reserved for his mother.我往往不相信自己的情感，倾向于把一切事...
颊窝毒蛇的毒牙是长的空心管子.The fangs of pit vipers are long, hollow tubes.只有四分之一的蛇具有毒液和毒牙.Venom and fangs are found in only a quarter of all known snakes.在蛇的进化史上,毒牙的出现是新的进步.A more recent advance in the evolutionary story of snakes i...