"Let's hide in the park quickly!"
Translation:공원에 빨리 숨어요!
cause the action is taking place somewhere else and the person suggests to go hide in the park.
"let's" usually translates in korean as the stem ..합시다 ...this isn't an option the multiple choice, so the closest correct translation is the imperative form.
I read your two comments. Let's is not fixed as '(으)ㅂ시다'.
하시지요, 합시다, 하세, 하자, 해요, 해 All can be possible. (by listener honorific level)