From Twitter:

A castaway* on a deserted island says:

"If I only had a lighter and a flare gun!"**

The suggested idea is (Choose):
a. He had only those things, but lost them.
b. He needs things--most of all those things, so then he could help himself with them.
c. He wishes he had just a lighter and flare gun.

*A castaway
is a person who has been cast (or "thrown", but not by someone else) away, meaning "lost" in a forgotten, hard-to-locate or distant and "uncivilized" place--away from society, such as a island in the Pacific Ocean.

**A flare gun fires a non-destructive glowing projectile (a flare) into the sky; 1. it is used to send an emergency signal in order for the user to show others his location, so that s/he can be found and rescued. 2. In war time it is used to illuminate where the enemy is.

Answer: The answer is b.: He needs things--most of all those things (the flare gun and lighter), so then he could help himself with them.

Explanation: The answer isn't a., because if only I had is a conditional clause expressing a wish for the present, not regret about the past. And the answer isn't c., because who would wish for only some necessary items and not others--and what would be the point of saying this in the narrative (story)?