To solve this question, the user needs to know basic grammar and verb agreement rules. In this sentence, the subject is "she," which is singular. Therefore, we need to use a singular verb form that agrees with the subject.
Now, let's go through each option and explain why it is right or wrong:
A. cook: This is the correct answer. "Cook" is the base form of the verb, and we add an -s to make it agree with the singular subject "she." Therefore, "She will cook my breakfast in the morning" is the correct sentence.
B. cooks: This is also a possible answer because "cooks" is a form of the verb that agrees with the singular subject "she." However, the question asks for the verb form that fills in the blank, and "cooks" is not the correct form to use in this sentence.
C. cooking: This is not the correct answer because "cooking" is a gerund, which means it is a verb form that functions as a noun. In this sentence, we need a verb form that agrees with the subject and shows the action that "she" will take.
D. cooked: This is not the correct answer because "cooked" is the past tense form of the verb, which does not fit with the future tense of the sentence. We need a verb form that shows that the action will happen in the future.
Therefore, the answer is: A. cook.