According to the air traffic rules, you should ________ off your mobile phone beforeboarding.
_____ he is very busy, he spends at least two hours every day surfing the Internet in order to find out the latest development in science and technology.
Several weeks had gone by _____ the head of the gallery realized the painting was missing.
The airline has a booklet _____ will tell you most of the important information to Europe.
Students can easily fall behind in their studies ____ they don’t manage their spare time carefully.
He warmly congratulated them on _____ they had achieved in science and technology.