阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填人一个适当的词或使用括号中词语的正确形式填空，并将答案填写在答题卡标号为16～25的相应位置上。

If you struggle against figures, maybe you were born that way, research has suggested. Being good at mathematics may be entirely pre-destined—you either have it   16  you don’t.

And those who find   17  difficult to add up the number shouldn’t feel too hopeless—mathematical talent does not appear to be linked to all-round intelligence. Previous research has indicated that "number sense" is    18   (base) to humans. We use it to estimate such things as    19   number of seats in a cinema or crowd sizes.

U.S. psychologists at Johns Hopkins University in Baltimore made their finding after testing children too young to have been taught mathematics. During the study, 200 four-year-olds   20  (study) in terms of number senses, calculation skills and vocabulary. The verbal test was done for the reason   21  language and maths abilities are thought to be   22  (close) linked through general intelligence.

"Unlike    23   previous studies proved, this one shows that the link   24  number sense and maths ability is already present before the beginning of formal maths instruction. One of the most important questions is whether we can train a child’s number sense   25  

(improve) his future maths ability."