The correct answer is **establish a scale**.

**Calibrate**

A. attest

B. conform

C. compute

D. establish a scale
The correct answer is (D) To establish a scale; to determine, test, or rectify the graduation of quantitative measurement instrument; to divide or mark with gradations, as on a meter, gauge, thermometer, etc. Also, determine the correct range, angle, or elevation for (a rifle, mortar, artillery gun, etc.) by observing where projectiles hit.

Calibrate comes from Arab galib (form).

Examples of use:

- They calibrated their measuring instruments before beginning.
- He used a set of standard weights to calibrate the balance.