3. (first picture answer options are the 4 graphs after it.)

The correct graph is attached below.

Step-by-step explanation:

Given:

Initial temperature is 0°.

Decrease in temperature per hour is 12°.

Since, the initial temperature is 0°, the line must pass through the origin as temperature is plotted along the y-axis.

Also, decrease in temperature per hour is 12°. So, this represents the slope of the line. So, the slope should be -12 as there is decrease in temperature with increasing time.

So, the correct graph will be a line passing through origin and the slope of the line must be -12. Also, the temperatures will be along the negative y-axis as the values are decreasing with time.

Hence, the third graph is the correct one and is shown below.