intense looks vs. dirty looks?

[Randy]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #558 "English Slang Idioms (196)", question 9

He was shocked at some of the clientele who wandered into his restaurant. He hoped, by providing the proper ambience, rich furnishings and high-priced specialty dishes he would keep the raucous riff-raff away from his business. Unfortunately, his latest customers had all been rude, inappropriately-attired college students that had the tendency to scare away the more refined diners and his ......... looks had not been enough to deter them from coming back.

(a) intense
(b) moody
(c) dirty
(d) fawning

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #558 "English Slang Idioms (196)", answer 9

He was shocked at some of the clientele who wandered into his restaurant. He hoped, by providing the proper ambience, rich furnishings and high-priced specialty dishes he would keep the raucous riff-raff away from his business. Unfortunately, his latest customers had all been rude, inappropriately-attired college students that had the tendency to scare away the more refined diners and his dirty looks had not been enough to deter them from coming back.

Correct answer: (c) dirty
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why not intense looks?

[Mister Micawber]

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It is not idiomatic, and it does not convey any clear meaning here.
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Native English teacher at Mister Micawber's