问题
选择题
Recently some studies have found that learning ____________ second language can lead to _______________ increase in one’s brain power.
A．a; the
B．不填; the
C．a; an
D．the; an
答案
答案：C
a +序数词表示再一，又一；an increase 一种增加，用做名词这个时候看作可数。