Step 1: Context.
The porter's mind is described as alert and sharp.
Step 2: Option Analysis.
(A) dull: Incorrect.
(B) average: Incorrect.
(C) sharp: Correct.
(D) intelligent: Not the phrase used.
Step 3: Conclusion.
Correct answer is (C) sharp.
“One of these days you’re going to talk yourself into a load of trouble,” her father said aggressively. What do you learn about Sophie’s father from these lines? (Going Places)