What is strange about the crypt is the following:
It is unlocked
This exercise is part of the reading comprehension activity about the story "Teen detectives".
In reading comprehension exercises, you have to read the story carefully and then answer the questions. Some tips for reading comprehension's exercises are to read the text once and then read the questions so you have an idea about what you are asked to answer. Then, you should read the text a second time and see if you can answer the questions.