The following sentence has been split into four segments. Identify the segment that contains a grammatical error.
I have read that / a Leaning Tower of Pisa is a / popular tourist attraction / in the world.

Correct option is B

Option (b) contains the error.
Correct phrase: the Leaning Tower of Pisa
Explanation:
· Use of “a” is incorrect before a proper noun that is unique and definite.
· "The Leaning Tower of Pisa" is a specific monument, hence the article “the” is required.
Grammar Rule:
Use ‘the’ before unique entities and specific names.
Example: The Eiffel Tower is in Paris.