The exam starts at9:00 tomorrow morning—___________ I failto arrive there on time

________ the 2020 Olympic Games will be held in Beijing is not known yet

Now there is a danger ________ the groundmay fall in under the heavy traffic.

“_____ when does the pub stay open” “About midnight”

_______it took 200 years to move from the steam engine to the Internet, there could be major development in _______ are now considered frontiers(尖端) of science in just the past few ten years.