In this chapter in Exercise 15.3question one (i), why can't we use bar graph and please also state that why we have used line graph to represent this data. please reply soon. my exams is in 2 days

A bar graph is used to show comparison among categories but a line graph display data that changes continuously over periods of time and in the question it is shown that the quantity is changing continuously ex. 5,10,15,20,25 . Thats why we are using line graph.Hope this will clear your doubt.