He has been working hard for 6 days，________a lack of concentration in the meeting.[ ]

Ann is in hospital.—Oh, really I ________ know. I ________ go and visit her.

My sister was writing an e-mail _______ I was watching TV at this time yesterday.

The chairman ________ hold office for five years according to the constitution.

The death of his devoted son was a painful experience, ______ he had never fully recovered.