meaning of "Tell someone off"

[Sajjad Qamar]

Test No. express/advan-4 "How Mary fell in love", question 8

Although he had never met her, he was determined to read her the riot act.

(a) tell her off
(b) tell her a story
(c) tell her straight
(d) tell her the truth

Test No. express/advan-4 "How Mary fell in love", answer 8

Although he had never met her, he was determined to tell her off.

Correct answer: (a) tell her off

Your answer was: incorrect
Although he had never met her, he was determined to tell her straight.
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What's the menaing of "tell her off ".
Please explain.

Sajjad Qamar

[Alan]

This means criticise someone for what they have done in a very direct manner.
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English as a Second Language
You can read my ESL story Womens' Day

[Eline2009]

Why can't it be "...he was determined to tell her straight" as in straighting things off