How Can the Windings Ratio Be Safely Determined for an Unmarked

Multiple Choice

How can the windings ratio be safely determined for an unmarked transformer?

A) Standardized wire color codes indicate windings ratio.
B) The turns ratio is the same as the ratio of primary resistance to secondary resistance ratio.
C) Apply known low voltage ac to the primary and measure the secondary output. The ratio of the voltages is the same as the windings ratio.
D) either A or C