Bicycling is good exercise; _______, it does not pollute the air

Would you please keep silent? The weather report______and I want to listen

His alarm clock didn’t this morning, so he was late for school.

Hiking trips ________ sound exciting to most kids, but few realize they ________ be uncomfortable and even dangerous. [ ]

With the fast development of computer and Internet technologies, traditional printed books ______ by the growing popularity of online reading of e-books