Think about where the phrase "catch a tartar" comes from before picking an option.
A Tartar (or Tatar) was a member of fierce Central Asian warrior tribes. Old war stories describe a soldier who bragged about bringing back a captured Tartar, only to find the Tartar fighting back so hard that the soldier could not let go or win. From that story, the idiom warns you might "catch" someone who turns the tables on you.
Option A talks about criminals and difficulty, which is too narrow and modern for this old idiom. Option D talks about disaster as a general outcome, but the idiom is specifically about grabbing hold of a person, not just bad luck. Option B, catching a dangerous person, stays close to the "fierce warrior" image in the story, so it lines up with the answer key.
Correct choice: B, to catch a dangerous person, based on the historical Tartar warrior image behind the idiom. Many dictionaries phrase this idiom as "to deal with someone tougher than you expected," which matches option C almost as well, so treat that as a close alternative reading.