【正确答案】Boys and girls have different incentives in math learning．

【答案解析】根据第3段第2、3句可知，数学成绩的性别差异不是源自资质的差异，而是学习动力的区别，所以答案为Boys and girls have different incentives in math learning。当然，也可以从女生或男生的角度去回答，比如The girls are more anxious about their future career或者The boys consider that fishing doesn’t necessarily need math。