Manyexperts believe that teachers’ development is _______ the key to bettereducation lies.

Help others whenever you can _______ youwill make the world a nicer place to live in.

It’s always difficult being in a foreign country, _____ when you can’t speak the language [ ]

The historicimpression on us．Every one of us thought their show was _________ a failure but a great success.

I was to co-operate without having moreinformation.[ ]