Find and correct the mistakes in the sentences. There is one

Find and correct the mistakes in the sentences. There is one mistake in each sentence.
1 The students havent seen all morning. Ive no idea where they are.


2 The exams were corrected for our teacher. I think they took her a long time!


3 The classroom is been painted at the moment, so we have to work in the main hall.


4 The question cant have answered. Its much too difficult!


5 The 3D film was been seen by thousands of people on its opening night.