you can see the slope of the graph is
5
9
, which means that for an increase of 1 degree Fahrenheit, the increase is
5
9
of 1 degree Celsius. Therefore, statement I is true. This is the equivalent to saying that an increase of 1 degree Celsius is equal to an increase of
9
5
degrees Fahrenheit. Since
9
5
= 1.8, statement II is true.
On the other hand, statement III is not true, since a temperature increase of
9
5
degrees Fahrenheit, not
5
9
degree Fahrenheit, is equal to a temperature increase of 1 degree Celsius.
The final answer is D.