Which one do u need help in?
Dr. Lanyon is an intelligent, respectable lawyer who is suspicious the "Mr. Hyde" is threatening or bullying Dr. Jekyll into giving him property and leaving money for him in his will. Because Dr. Lanyon is an intelligent man, he always looks for a logical, practical answer, which is why he does not wonder is Hyde and Jekyll are the same person.
You did not include options in your question, but based on the meaning of the word cryptic, your answer will be 'A HIDDEN MEANING'.
When you say that something is cryptic, it means that, that thing has a meaning that is mysterious or obscure.
From the way the word was used in the given sentence, it means that the message the teacher was passing across about the test is hidden, it was not understood by any of the students.