The answer is A because it tells the workmen were worked hard.
Hello,
The answer is option A "they".
Reason:
Pronouns are talking about more than one verb for example: they, we, and them. Therefore your answer is A because its the suitable fit for the sentence.
If you need anymore help feel free to ask me!
Hope this helps!
~Nonportrit
1) The decline of the American Dream in the 1920s
2) The Hollowness of the Upper Class
3) The Valley of Ashes
I hope that's help !