While there are some differences in the educational systems in many countries in the world，education is ________.[ ]

So many floods have cut down on the production of peanuts; _______, the price has gone up a great deal.

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

It’s recommended that our plan _____ until it was tested again.

Is it necessary that he ____ to London but to New York?– I think so, but the problem is ____ he has refused to.