8. When Harry and his mother went in, his father (SIT) on the sofa with a remote control in his hand but the TV was off.

Solution:

The sentence describes an ongoing action in the past when Harry and his mother entered. The past continuous tense is appropriate. The subject is 'his father' (singular), so the past continuous form is 'was sitting'.

Answer: 8. When Harry and his mother went in, his father was sitting on the sofa.