登山时，将喝空的矿泉水瓶拧紧瓶盖。下山后瓶子变瘪，瓶内的气体分子

A．体积变小

B．个数变少

C．间隙变小

D．质量变少．

______ my little brother is a child , he knows a lot.

A．Even

B．If

C．Even though

D．Until