To solve this question, the user needs to know the correct subject-verb agreement in a sentence. The user should identify the subject of the sentence and make sure that the verb is in the correct form to match the subject.
In this sentence, the subject is "our firm," which is singular. Therefore, we need a singular verb form to match it.
Now, let's go through each option and explain why it is right or wrong:
A. did: This option is incorrect because "did" is the past tense of "do" and doesn't match the singular subject "our firm."
B. do: This option is incorrect because "do" is the present tense of "do" and doesn't match the singular subject "our firm."
C. does: This option is correct. "Does" is the third-person singular present tense of "do," and it correctly matches the singular subject "our firm."
D. done: This option is incorrect because "done" is the past participle of "do" and is not a verb form that can be used in this sentence.
Therefore, the correct answer is:
The Answer is: C. does