Sara kept the secret to ________ and nobody knew about it.

How careful Jim is! – He writes ____ in our class.

Cathy, are you going to buy a flat in Shanghai? —You must be joking. I can’t __________ one there.

It is _______ difficult for us _______ climb up the mountain.[ ]

I failed in the final exams last term and only then____the importance of study.[ ]