1. He built a fire in/on the mountain.

2. He made a fire in/on the mountain.
3. He started a fire in/on the mountain.
4. He lighted a fire in/on the mountain.
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Can we use all the verbs? Are they the same? What about the prepositions? Can we use both prepositions?

5. He set a house on fire.
6. He set a house on a fire.
7. He set fire to a house.
8. He set a fire to a house.
(Do we have to put 'a' before 'fire'? Which ones are correct?)

In the first one, all the verbs can be used, and are used. One does not build a fire IN a mountain, unless it's inside a tunnel. If it's above ground, it's ON the mountain.

No, "a" is misused in 6 and 8. You may set a house afire. "Afire" means the same as "on fire". You may set a fire near the house, on the roof of the house, etc., but you set fire to a house, you set a house on fire, or afire.

1. He built a fire in/on the mountain.

2. He made a fire in/on the mountain.
3. He started a fire in/on the mountain.
4. He lit a fire in/on the mountain.

Regarding the verbs, all of them are grammatically correct and can be used interchangeably to convey the idea of creating a fire. However, there are subtle differences in meaning:

- "Built a fire" implies constructing or assembling the fire, suggesting a deliberate and planned action.
- "Made a fire" implies creating or producing a fire, indicating a more general action.
- "Started a fire" implies initiating or causing a fire to begin, suggesting that the fire was intentionally ignited.
- "Lit a fire" implies setting a fire ablaze or igniting it, indicating a specific action of providing flame or heat to the fire.

As for the prepositions, both "in" and "on" can be used, depending on the intended meaning:

- "In the mountain" suggests that the fire is contained within the mountain or within a specific area on the mountain.
- "On the mountain" suggests that the fire is located somewhere on the surface or slopes of the mountain.

5. He set a house on fire.
6. He set a house on a fire.
7. He set fire to a house.
8. He set a fire to a house.

In this case, the correct phrases are:

- "He set a house on fire": This means that he caused a house to ignite and be engulfed in flames.
- "He set fire to a house": This means that he intentionally started or caused a fire to occur at a house.

The phrase "He set a house on a fire" is not grammatically correct. It should be "He set a house on fire."

Regarding the placement of "a" before "fire," it depends on the specific phrase used:

- "Set a house on fire" and "set fire to a house" are both grammatically correct.
- "Set a fire to a house" is not the typical or preferred usage. It would be more common to use "set fire to a house" to convey the meaning of intentionally starting or causing a fire at a house.