Read the following context and choose the best option to answer the question.
Context: I took her to the vet on Saturday 'cause they would n't give me antibiotics w/o seeing her . It was all rather easy considering what a pain Trigger at the vet is . Well unfortunately the antibiotics have made her have the runs again . And for some reason when she has the runs she can not do it in the litter box .
Question: Why did their cat need to see the vet ?
Options: 
A. Their cat kept throwing up in the litter box .
B. Their cat was unable to use the bathroom .
C. Their cat was suffering from diarrhea .
D. None of the above choices .


C