Another question on critical reasoning?

I made this up myself, so please dont mind if none of the options are correct. There are two section for 11th standard in Bal Bhawan School - 11th A and 11th B. Since the new class teacher came for 11th A section, the results of 11th A has been deteriorating. Since all other teachers are same for both the sections, this must be because of the new class teacher. Which of the following statement will weaken the argument above? A. The new class teacher for class 11th A is from IIT, a reputed college B. Since the new teacher has arrived for class 11th A, most of the students in the class have been suffering from viral fever C. Students in section A can run faster than students in section B critical-thinking