試題詳解

17.Our bodies need food and oxygen, and these must be supplied constantly. Food can be stored in the body, so a person need not eat all the time in order to satisfy this requirement. Our bodies cannot store oxygen; therefore, _____.
(A) food is harder to find than is oxygen
(B) we must keep looking for new supplies of oxygen
(C) we must keep breathing all the time
(D) oxygen is more important than food