I told him not to play … fire.

Analyze the question: The sentence is "I told him not to play ____ fire." We need the correct preposition that goes with the verb "play" in this idiomatic expression.

Explain the concept: In English, some verbs go with specific prepositions. The idiom "play with fire" means to do something risky or dangerous. It is a fixed expression, so the preposition cannot be swapped for another.

Step-by-step solution:

1. A. on: "play on fire" is not an accepted expression. It would suggest playing while standing on a burning surface.
2. B. with: "play with fire" is the correct idiom. It means to take part in a dangerous activity or take unnecessary risks.
3. C. beneath: "play beneath fire" makes no sense in this context.
4. D. upon: "play upon fire" is wrong. "Play upon" exists, as in "play upon someone's fears", but not with fire.

Correct sentence: I told him not to play with fire.

Tip: Learn common idioms as complete phrases rather than as separate words. Some examples are "play with fire," "break the ice," and "hit the nail on the head." In WASSCE, preposition questions usually test fixed expressions, so ask yourself, "Have I heard this phrase before?"