Final answer:
An unfavorable flexible budget variance in variable costs indicates an increase in variable cost per unit, not changes in sales prices, sales volume, or fixed costs.
Step-by-step explanation:
An unfavorable flexible budget variance in variable costs suggests a(n) increase in variable cost per unit. Variable costs are those that vary with output, such as labor and raw materials. When output increases, variable costs also increase because more resources are needed to produce more goods or services. Conversely, if the variable costs per unit increase while output stays the same, this will result in an unfavorable variance, implying that the costs to produce each unit have gone up. This can happen due to increases in the price of raw materials or wages. It's important to note that unfavorable variances are not associated with changes in sales price per unit, sales volume, or fixed costs, which are handled separately in budget analyses.