Concept:The expression compares air to burning gas directly, with no word such as "like" or "as" to soften the comparison.
Explanation:The poet writes that "the air was actually burning gas."
This suggests the heat is so extreme that the air itself seems to be on fire.
Because the statement identifies air with burning gas instead of merely saying it is similar, it is an implicit comparison.
An implicit comparison of two unlike things is known as a metaphor.
A simile would use "like" or "as"; personification would give the air human qualities; a paradox would seem self-contradictory.
The image strongly conveys the intense, suffocating heat felt by the character.
Answer:C. metaphor