Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions.
The substance is very toxic. Protective clothing must be worn at all times.
A. Since the substance is very toxic, so protective clothing must be worn at all times.
B. So toxic is the substance that protective clothing must be worn at all times
C. The substance is such toxic that protective clothing must be worn at all times
D. The substance is too toxic to wear protective clothing at all times