I just don’t understand ______ that leads toso many teenagers becoming addicted to playing computer games.

Some scientists think there are _______ 2，000 million flashes of lightning per year

下列说法有误的一项是（ ）

Jack, could you help me ________ these pictures on the blackboard It may help us knowmore about the hazy weather. (雾霾)— With pleasure.

It is easy for people to ________ the bad habits such as smoking and drinking, which are not so easy to get rid of.