Concept:The idiom "Jump the gun" means to start something too early or without proper preparation.
Explanation:The phrase comes from a race where starting before the signal is a mistake.
It refers to acting before the right time.
Example: He jumped the gun by announcing the news before it was confirmed.
This matches the meaning of "Act prematurely".
The other options are not correct: "Succeed quickly" is about fast success, not early action.
"Wait patiently" is the opposite meaning.
"Fire a gun" is the literal meaning, not the idiom.
Answer:Option B: Act prematurely