Final answer:
The correct answer is option a. The most crucial factor in investment decisions is the change in after-tax cash flow, which represents the real profitability after considering all costs and taxes. Future profit expectations, tax policies, and interest rates are also significant in determining investment attractiveness.
Step-by-step explanation:
When making investment decisions, various factors are considered to deduce the expected profitability of the investment. The most important factor is likely A) The change in after-tax cash flow, as it directly measures the net value an investment generates, taking into account not just gross revenues or income, but also expenses, depreciation, and crucially, taxes, which can significantly affect the net return on investment.
Expectations of future profits, changes in economic conditions, the role of government incentives or tax policies, and interest rates are also influential as they can dictate the overall attractiveness and the opportunity cost of investments.