The temperature starts at 50°, then it slowly increases. Next it increases quickly, then it stays the same temperature for an hour. And finally the temperature slowly decreases.
The 1st graph is your answer(top left)
It is not the 2nd graph (top right) because the temperature stays at 50° for 2 hours, than decreases, which does not match the description.
It is not graph 3 (bottom left) because it increases quickly, than stays the same for 4 hours.
It is not graph 4 (bottom right) because the graph is decreasing most of the time
