已知集合 A={x∣x>2}A = \{x \mid x > 2\}A={x∣x>2},B={x∣x>a}B = \{x \mid x > a\}B={x∣x>a}。则“a<2a < 2a<2”是“A⊊BA \subsetneq BA⊊B”的( )