Step 1: Spot the clue in the case:
The passage points out one specific benefit of a loan: its interest is allowed as a deduction while computing tax.
Step 2: Recall the related idea:
A deduction means a smaller tax payment. So after tax, a loan costs the firm less than what it pays as interest. The size of this benefit depends on the rate of tax. Before marking the answer, compare the key phrase of the case with the meaning of each option once more. Words that sound alike can mislead, so match meaning and not sound. Only one option fits both the case and the definition.
Step 3: Test option (A).
Inflation is about rising prices. The passage does not use it to explain cheap debt, so we drop it.
Step 4: Test option (B).
The tax rate fits well, as the interest shield works through it. We keep it.
Step 5: Test option (C).
Growth prospects relate to future expansion and not to the price of a source. We drop it.
Step 6: Test option (D).
This is not a named factor and gives no reason for low cost. We drop it.
Final Answer:
The tax benefit on interest makes debt cheap, so the factor is the tax rate, option 2.
\[ \boxed{\text{Option 2}} \]
