-  ‘a long time’ in place of ‘the long tome’

The given sentence is in the past tense, and it talks about an action that was completed in the past. Hence, the present perfect tense "have been awaiting disposal" is not appropriate here. Instead, the past perfect tense "had been awaiting disposal" should be used to indicate an action that had been going on in the past and was completed before the past action "started working" began.

Therefore, the correct sentence would be "that had been awaiting disposal for a long time."

The correct sentence after correction:

Having finished his breakfast (1)/ he started working (2)/ on the problem (3)/ that had been awaiting disposal for a long time. (4)/ No error.

To summarize:

• The error in the given sentence is in Part 4: "that have been awaiting disposal for the long time."
• The present perfect tense "have been awaiting disposal" is not appropriate here as the sentence is in the past tense.
• The past perfect tense "had been awaiting disposal" should be used to indicate an action that had been going on in the past and was completed before the past action "started working" began.
• Therefore, the correct sentence is "that had been awaiting disposal for a long time."
• Hence, the answer is option D: 4.

If you think the solution is wrong then please provide your own solution below in the comments section .