Resolved: Ambiguous options in the final exam (that with 24 questions)

I'd like to report some problems. I take as example the first question: if the question is "which of the following statements is correct?", I suppose that just 1 answer is correct, otherwise I could choose multiple answers. Instead, one of the option is "a) is true and b) is false", and it is correct, but also option "a)" is correct. So why the option "a) is true and b) is false" should be more correct than just option "a)" or viceversa? They are both correct.
Furthermore, I think that 40 minutes is too little time to perform the calculations required in other questions.
Thank you.