The correct answer is C. It is correct, because it indicated that Callie is not friendly today.
Step-by-step explanation:
According to grammar almost always there should be an agreement between the subject and the verb which means if the subject is singular the verb should also have a singular grammatical form. However, there are some exceptions to this, one of this is the use of "were" as if the sentence is a conditional sentence or expresses an unreal state by using expressions such as would like or wish, "were" should be used for all subjects no matter if these are singular or plural as it does not refer to the past in which was is used with the nouns "I, he, she and it" and were is used with "You, they and we", but to an unreal state which is grammatically different. Considering the sentence "The teacher says that he has noticed a change in Callie" refers to an unreal state as Callie is not friendly today, but the speaker would like her to be friendly in that day it is correct to use "were" even if Callie is singular because it refers to a situation or desire that is not real.