Understanding Variable Costs Steps:

• Define variable costs as expenses that fluctuate directly with production volume, like materials or labor.
• Note that total variable costs rise proportionally with output, while per-unit cost stays fixed.
• Compare each option to this definition to identify the best match.
• Select the option describing constant per-unit behavior across output levels.

Why B is correct:

• Variable costs follow the formula Total VC = Variable cost per unit × Output, keeping per-unit cost constant over any output level.

Why the others are wrong:

• A describes step costs, which remain fixed in blocks before jumping, not continuously variable.
• C describes fixed costs, with total amount unchanged regardless of output.
• D describes increasing marginal costs, where per-unit expense rises with higher output due to inefficiencies.

Final answer: B