42 We ....... for three hours before we decided to take a break. A must be trekking B had been trekking C have been trekking

Solution:

• The sentence describes an action that was in progress for a duration in the past before another past action occurred.
• This requires the past perfect continuous tense.
• "Had been trekking" correctly uses the past perfect continuous to indicate a continuous action that was completed before another past event.

Answer: B had been trekking