Final answer:
The sentence that uses the word 'syntax' incorrectly is: 'Johnny had to syntax his room before he could leave the house.'
Step-by-step explanation:
The sentence that uses the underlined word incorrectly is: Johnny had to syntax his room before he could leave the house. The incorrect usage of the word 'syntax' in this sentence suggests that Johnny had to organize or arrange his room before leaving, which is not the correct meaning of the word. 'Syntax' refers to the rules and structure that govern the arrangement of words and phrases in a language or programming code, not the cleaning or tidying of a room.
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