When dealing with an interval scale such as fahrenheit temperature, it is correct to say
a. the difference between 90 and 30 is three times the difference between 40 and 20
b. 60 is three times as hot as 20
c. both a and b are correct
d. none of the above are correct

(c) both (a) and (b) are correct

Explanation:

Let take the temperature first 90°F and 30°F

Then the difference between the temperature = 90°F-30°F=60°F

Now the temperature is given as 40°F and 20°F

Then the difference between the temperature = 40°F-20°F=20°F

We can see that 60 is 3 times of 20 so option (a) will be correct

Now as the heat is linearly dependent on the temperature as so at 60°F it will be 3 time hotter than at 20°F

So option (b) is also correct as option (a) and (b) are given in option (c) so option (c) will be the correct option

i believe the answer would be:

d. violin, clarinet, french horn, and tuba