Are pupils doing grammar exercises at the moment?
What are pupils doing at the moment?
When are pupils doing grammar exercises?
Are pupils doing grammar exercises or reading at the moment?
Pupils are doing grammar exercises at the moment, aren't they?
a charter flight is less expensive than a other flights because it is performed for a specific customer-<span>чартерные рейсы</span><span> </span><span>дешевле, чем</span><span> </span><span>другие рейсы</span><span>, поскольку она</span><span> </span><span>осуществляется </span><span>под конкретного заказчика</span>
В обоих предложениях верный вариант вопроса 2.