The correct answer is C. colossal.
A colossal loss is a very large loss. It is a loss that is so large that it is difficult to comprehend. The strike in the paper mill has resulted in a colossal loss because it has caused the mill to shut down and many people to lose their jobs. The loss of income from the mill has also had a negative impact on the local economy.
The other options are not correct because they do not accurately describe the loss that has been caused by the strike. Option A, commendable, means worthy of praise. Option B, voluminous, means large in amount or extent. Option D, comprehensive, means complete or thorough.