SUBJECT-VERB AGREEMENT PROBLEM
VERB SHOULD BE SINGULAR
SO ONLY OPTIONS A AND D QUALIFY
HOWEVER IN A,THE 2ND PART OF THE SENTENCE HAS A SUBJECT VERB PROBLEM
"WHAT IS MORE DIFFICULT " IS SINGULAR SO VERB SHOULD BE "IS"
sorry man, but I don't agree to your point. This is composite sentence and PERIOD is the subject in 1st sentence. The period ..... has been,
in the second sentence there is or are
... WHAT IS MUCH MORE DIFFICULT TO DETERMINE
or THE USE, THE REASON AND THE MEANING.
The greatest pleasure in life is doing what people say you cannot do...