Answer: B) The landlord put the key back on the counter that he uses to unlock the front door.
Explanation: a misplaced modifier is a phrase or clause placed awkwardly in a sentence so that it appears to modify or refer to an unintended word. From the given options, the sentence that contains a misplaced modifier is the corresponding to option B: The landlord put the key back on the counter that he uses to unlock the front door, in this sentence the misplaced modifier is " that he uses to unlock the front door" (and it isn't clear if it is modifying "key" or "counter"), so the correct sentence would be "The landlord put the key that he uses to unlock the front door, back on the counter."
