To read a 45-degree angle on a drafting machine, which part should the protractor be aligned with?

The appropriate way to read a 45-degree angle using a drafting machine involves aligning the protractor with the correct reference point on the scale. When you want to measure an angle, the protractor should be positioned so that the 0 mark aligns with the baseline or reference line from which you are measuring. By aligning the 0 on the vernier plate with the baseline, you ensure that the angle measurement starts correctly from that reference point.

In this case, a 45-degree angle means that as you move away from the 0 mark on the vernier plate, you will find your desired angle precisely at 45 degrees. This setup ensures that any additional angle measurements taken from that reference will be accurate, as the protractor's alignment directly influences the precision of the angle readings. Thus, this is why aligning the 0 on the vernier plate is the correct choice for reading a 45-degree angle.