When the teacher entered the class, we <u>had</u><u> </u><u>finished</u> our work.
Therefore, C - Had Finished is the correct answer.
<h3>Using the right Tense</h3>
The sentence above has two events. They are:
- The teacher entering the class.
Notice that both occurred in the past. The rule of proper use of verbs states that where both events have occurred, and one before the other, the proper tense to use is the past perfect tense.
See the link below for more about Past Perfect Tense:
brainly.com/question/4161654
Coexist means that they live together or they are used together. Therefore, they coexist with one another. The answer would be C.
I hope this helps!