Final answer:
A firm is likely to increase short-term debt relative to long-term debt when short-term rates are high but expected to decrease, allowing the firm to refinance at a lower cost in the future.
Step-by-step explanation:
A firm will usually increase the ratio of short-term debt to long-term debt when the term structure of interest rates is inverted and expected to shift down, which is option B. This situation means that short-term borrowing costs are currently higher than long-term borrowing costs but are expected to decrease in the future. Firms might capitalize on this expectation by taking on more short-term debt currently, with the plan to refinance at a lower rate when the rates fall, thus reducing their overall borrowing costs over time.