먼저 수특 3강 4번 보면 they possess a second stomach called a rumen- a roughly forty-five-gallon tank in which resident bacteria convert cellulose into protein and fats여기서 convert가 왜 converts로 안쓰인거죠?? ㅠㅠ 또 in which 전치사+관대인데 by which in which 뭘 써야하는거죠??