(2010 the first mock exam in Fengxian District) sets A={(x, y) |x24  +y216=1}, B={(x, y) |y=ax, a > 0, a a, then the number of subset of the subgroup is () A. 2B. 3C. 4D. 1

(2010 the first mock exam in Fengxian District) sets A={(x, y) |x24  +y216=1}, B={(x, y) |y=ax, a > 0, a a, then the number of subset of the subgroup is () A. 2B. 3C. 4D. 1

It can be seen from the meaning that set a and B have two intersections, so the number of subsets of a ∩ B is: 4