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.
Machines can serve as both a help and a hindrance!
Answer:
You can (should) never say yes to a strange man who offers you candy!
:b
Having a vivid picture of a setting, person, object etc and the ability to create a detail and clear description of said thing or said person. But that's just what I think.