A different route to the same answer is to work from the back of the week forward. Let's see how each option holds up:
Once Mathematics, Chemistry and Biology are fixed in the back half of the week, only the front three days remain for Physics, Play and Social Science, and the play day always lands in the middle of that stretch, Tuesday.
Therefore, the correct answer is Tuesday.
Rather than counting days by name, we can count how many other activities from the schedule fall between Physics day and Biology day.
Since Play, Social Science, Mathematics and Chemistry each occupy one of the four days lying between Physics day and Biology day, the gap between them is four days.
Therefore, the correct answer is Four.
We can also anchor this from the other end of the week, using Biology's fixed position instead of the play day.
Anchoring from Biology's fixed Saturday position and counting the required two-day gap back places Social Science on Wednesday, consistent with every other clue.
Therefore, the correct answer is Wednesday.
Clue (iv) alone gives us three separate conditions for Mathematics day: it cannot be the first reading day, it cannot be the last reading day, and it must fall before Chemistry day. Let's apply these directly to each option:
Testing clue (iv)'s three conditions directly against each day shows Thursday is the only one that clears all of them while also being free once the other five activities are placed.
Therefore, the correct answer is Thursday.
A quicker route here is to notice that one of the four options is worded almost exactly like one of the original clues, so it can be confirmed without building the whole schedule at all.
Because one of the four options is simply a restatement of clue (v) itself, it can be confirmed as true immediately, while the other three each contradict the schedule once it is worked out.
Therefore, the correct answer is Biology day is after Chemistry day.