Identify the segment of the sentence which contains a grammatical error.
Sentence: Shall her flight get cancelled, your mother says she will send you a message.

Correct option is C

Option (c) contains an error.
Error Explanation:
The error lies in the use of “Shall” at the beginning of a conditional sentence.
"Shall" is a modal verb typically used to express futurity, strong intention, or suggestion, but not to introduce conditional clauses.
Conditional clauses starting a sentence should use “If” or “Should”, not “Shall.”
Correct sentence:
If her flight gets cancelled, your mother says she will send you a message.
OR
Should her flight get cancelled, your mother says she will send you a message.
Grammatical Rule Used:
In conditional sentences:
Type 1 (real condition):
Structure: If + present simple, will + base verb
Correct: If it rains, we will stay indoors.
Inversion form (formal/advanced):
Structure: Should + subject + base verb, 
Correct: Should he arrive late, start the meeting without him.
Incorrect: Shall her flight get cancelled… → Incorrect usage of "shall" for condition.
Additional Tip:
"Shall" is typically used with "I" and "We" in legal/formal British English contexts:
Correct: I shall return by evening.
Incorrect: Shall her flight get cancelled… → sounds awkward and grammatically incorrect.