Final answer:
The correct answer is A) Dividing the elongation of the gage length of the specimen by its original length, which is how the average strain in a tension test is calculated.
Step-by-step explanation:
The average strain in a tension test is calculated by dividing the elongation of the gage length of the specimen by its original length. This means that if the initial length of the specimen is L0 and after applying a tensile force it elongates by ΔL (where L is the new length), the strain (ε) would be the ratio ΔL / L0.
Therefore, the correct answer to the question is "A) Dividing the elongation of the gage length of the specimen by its original length". This measure of strain is unitless since it is the ratio of two lengths. It's important to clarify that the strain is a measure of deformation under tensile stress and does not involve multiplying by one hundred or involving the load or cross-sectional area directly.