The following sentence has been split into four segments. Identify the segment that contains a grammatical error.
They missed their train / because they were waiting /on wrong platform. / They were on platform 3 instead of platform 8.

Correct option is B

Option (b) contains an error.
The segment "on wrong platform" is grammatically incorrect because it lacks the necessary article "the" before the adjective "wrong."
In English, definite articles are used before adjectives like "wrong" when they precede a noun to specify or clarify the noun. The corrected phrase should read "on the wrong platform." Grammatical rule used: Articles ("the," "a," "an") are typically used in English to indicate specific or general items, and in this case, "the" is required to indicate a specific platform that was incorrect or not intended.