Here are the correct answers to the questions you provided:
Cambridge is one of b) the oldest universities in Europe.
I found my visit to the museum a) more interesting than I expected.
This letter b) won't be sent until tomorrow.
This work d) was finished in 2015.
My favourite book a) was written by Pushkin.
You will be sent a present. c) Тебе пошлют подарок.
She was offered help. c) Ей предложили помощь.
He didn't go to a) the/the college, because he was ill. He saw still in the bed.
His elder brother is in the prison now. We are going to visit.
Feel free to ask if you need help with anything else!