Thanks for the question! So in this question, we’re assuming that First Street is cleaned earlier than Third Street, and then finding out which statement has to be false.
OK, well recall that we have 5 days and 2 slots per day, morning and afternoon. We know that 4th Street is cleaned on Tuesday morning, and 7th Street is cleaned on Thursday morning. We also know that 8th Street was cleaned on an afternoon, and before 4th Street (cleaned on Tuesday), which means it was cleaned on Monday afternoon.
Now we should ask ourselves: who can be cleaned on Monday morning? Well, 2nd and 5th Street are cleaned on afternoons from rule 6. We’ve already placed 7th, 4th, and 8th Street. And we know that 6th Street is cleaned after 4th Street (cleaned on Tuesday morning) from rule 5, which means 6th Street can’t be cleaned on Monday. Which means that the only options for Monday morning are First Street and Third Street.
Well, now we’re assuming that First Street is cleaned earlier than Third Street. And Monday morning is the earliest possible, which means that Third Street can’t be on Monday morning, because then First Street wouldn’t be earlier than it. So First Street has to be cleaned on Monday morning. This, of course, means that First Street can’t be cleaned on Tuesday afternoon, and so that must be false and (A) is the answer to this question.
Hope this helps! Feel free to ask any other questions that you might have.
