Ben goes to work ________ and his sister goes to work ________.
A：by car; on her bike
B：by a car; on her bike
C：by cars; by bikes
D：by his car; by bike
下列现象中，属于不文明行为的是（ ）
为了办好2010上海世博会，上海有关部门对汽车尾气进行检测．此举的主要目的是为了减轻（ ）
Can you swim?（做出肯定回答）
____
