Final answer:
The statement is incorrect because of the wrong verb tense and the implication that the detectives were previously dangerous criminals. Correcting grammar and punctuation errors is important in English to ensure clear communication.
Step-by-step explanation:
The statement 'They weren't dangerous criminals they were detectives in disguise' is incorrect because it uses the wrong verb tense and implies that the detectives were previously dangerous criminals. To correct this statement, it should be rewritten as 'They were not dangerous criminals; they were detectives in disguise.'
Using the correct verb tense and punctuation helps to convey the intended meaning. In this revised statement, it is clear that the individuals were detectives all along and not dangerous criminals. Correcting grammar and punctuation errors is important in English to ensure clear and effective communication.