There is no simple answer, _____ is often the case in science.
| A．as | B．that | C．when | D．where |
Find ways to praise your children often, _________ you'll find they will open their hearts to you.
| A．till | B．or | C．and | D．But |
Only when _______ be possible to sign the papers.
| A．does the lawyer come with it |
| B．the lawyer comes will it |
| C．has the lawyer come it will |
| D．the lawyer comes it will |
-What has made him in such a low mood recently?
—_________ by his father for not passing the exam.
| A．Being criticized | B．Criticized |
| C．Having criticized | D．To criticize |
The government _____ air quality in urban areas from level one to five: excellent, fairly good,slightly polluted, poor and dangerous.
A arranges B. classifies C. distributes D. divides
The real-name policy for train tickets has been applied to all trains since January l, 2012 in China,________ will make it easy for people to get tickets.
| A．which | B．when | C．what | D．Where |