IAL Jan 2019Unit 1 MCQ 10

Hi
This question has baffled me, help me understand the correct answer. It's a graph question and i don't know whether i can post a graph here but this is the link to the paper.

https://qualifications.pearson.com/content/dam/pdf/International%20Advanced%20Level/Chemistry/2013/Exam%20materials/WCH01_01_que_20190110.pdf

That’s an extrapolation question.

Start by drawing a vertical line at t = 3 1/2 minutes.

Draw a straight line that passes through all the points between t = 0 and t = 3 1/2 minutes. This will be a horizontal line corresponding to the initial temperature of the solution.

Now draw a straight line through all the points from the 5 minute mark to the 12 minute mark, as these points lie in a straight line. Extend this line back as far as the vertical line at t = 3 1/2 minutes. The point at which this extended line meets the vertical line at t = 3 1/2 minutes corresponds to the extrapolated maximum temperature.

The difference between your extrapolated maximum temperature and initial temperature will be your temperature rise.