Question

Which of the following is not part of necessary outdoor preparations.? A:Tell someone where you’re going. B:Make sure your cell phone is charged. C:Check the weather forecast. D:Pack enough food and water.

Answer 1

Answer: Make sure your cell phone is charged.

Answer 2

I would say B.
A is important because your friends and family may report you missing.
C is important because you don't want to be caught outside in a storm.
D is important for obvious reasons.

You don't necessarily need your cell phone and the question is asking what is NOT necessary.