Hey,

The Multiple selective question means that the correct options can be more than one but it's not the necessity that it has to be more than one. Some MSQs may have only one option as a correct answer.

The question you are talking about might have only one correct option that's why it's showing only one option in the official answer key. Even after that if you find that the question is incorrect don't worry if proven wrong you will definitely get bonus marks for that.

All the best

Thank you.