Experts are trying to work out a plan to deal with the problems caused by global warming _________ it is too late

The research on the new flu virus vaccine ischallenging and demanding Who do you think can do the job —_______ my students have a try

If human beings had been a bit less greedy and cruel, more birds and animals _____dying out.

The elderly need special care in winter, as they are ______ to the sudden change of weather.

Not until I ________ to work ____ how muchtime I had wasted.