Final answer:
The incorrect sentence is C. 'Everyone wanted to share their observations.'
Step-by-step explanation:
The correct answer is C. The sentence 'Everyone wanted to share their observations' is incorrect because the pronoun 'their' does not agree in number with the noun 'everyone'. The correct pronoun to use in this case would be 'his' or 'her' to match the singular noun 'everyone'.
Learn more about Subject-Verb Agreement