Fill in the blank (_) in the following sentence from the following choices.
Sentence: Since I took the books out of the box and put them into the storage chest, the _ became very light.

Choice 1: Since I took the books out of the box and put them into the storage chest, the box became very light.
Choice 2: Since I took the books out of the box and put them into the storage chest, the chest became very light.
Which of the choices is correct? Respond with only "1" or "2" and no additional text.
1
1.