Answer :
The sentence which is correct is C) To get inside , you must unlock the door.
The sentence "To get inside, you must unlock the door." is correct because it clearly states the action needed to achieve the goal of entering a space. It begins with “To get inside,” setting up the purpose or condition, and follows with “you must unlock the door,” which specifies the required action.
The sentence is grammatically correct, concise, and directly communicates the necessary steps to gain entry. It effectively combines the purpose and action in a straightforward manner, making it easy to understand and follow.