We ...don't know this rule very well.2.Nick ..doesn't . swim very often.3.Ann .isn't .. singing at present4.The boys ... don't often ride) their bikes5.My friend ... isn't playing his computer now6.They ... (aren't choosing a present right now7.I ...don't swim) everyday8.Tom ..isn't . (sending) an e-mail now9.My sister ..doesn't . (draw) her dog everyday10.I ..don't . (cook) the dinner every Sunday11.The girls ..don't . (draw) newspapers on Fridays12.Two brothers ..aren't . (playing) basketball now