Tell me the reason why/that you're always late.

[Andy Lin]

Source from Lai's ENGLISH GRAMMAR authored by Shixiong Lai.

Tell me the reason ____ you're always late.
(A) why (B) that

Author said A is correct answer without explanation.
I wonder why B can not?

 

[emsr2d2]

Source: from Lai's ENGLISH GRAMMAR authored by Shixiong Lai.

Tell me the reason ____ you're always late.
(A) why (B) that

The author said A is the correct answer, but without any explanation. I wonder why B can is not correct.

Note my corrections above. Italicise book titles. Keep it simple. The source should be written like this:

Source: Book Title by Author's Name

Remember to use articles where appropriate. As it stood, your sentence said that "A" = "correct answer without explanation". That's not the case. Think hard about what meaning the reader will get. A sentence that starts with "I wonder" is not a question.

Both are possible, as is using nothing between "reason" and "you're". It's a poor test question. I would say "Tell me why you're always late" or "Tell me the reason you're always late" but those are just personal choice. You'll find that some teachers don't like learners to use "reason why", claiming it's tautologous. However, it's grammatically correct, as is "reason that".

The problem with English grammar books that are written by non-native speakers is that the authors sometimes think there's just one correct answer, and it turns out they're wrong.

 

[tedmc]

My preference is for "reason you are late". "Why" in "reason why" is redundant, as emsr2d2 pointed out, though it is often used. It is like saying "discuss about", when "discuss" means "talk about". "That" following a subject is often omittable.

 

[5jj]

It is like saying "discuss about", when "discuss" means "talk about". "That" following a subject is often omittable.

Not quite. 'Discuss about' is incorrect and unnatural. 'Reason why' is commonly used and widely accepted.