Under the life cycle approach to portfolio planning, investors with longer time horizons can normally accept higher equity allocations because they have more time to withstand volatility and recover from market declines. Personal commitments also matter because high family or financial obligations reduce risk capacity. Investor D has long-term investment goals and only moderate personal commitments, making this investor better positioned to hold or increase equity exposure. Investor A has light commitments but a short-term goal, which limits equity suitability. Investor B has both short-term goals and high commitments, making equities least suitable. Investor C has a medium-term horizon and moderate commitments, but still has less risk capacity than Investor D. Therefore, Investor D is the best answer.

The debt-to-equity ratio reveals the nature of a company's capital structure by comparing the amount of financing supplied by creditors with the amount supplied by shareholders. A higher debt-to-equity ratio indicates greater leverage and greater reliance on borrowed funds. This can increase return potential when business conditions are favourable, but it also increases financial risk because interest and principal obligations must be met. Price-to-earnings is a valuation ratio, not a capital structure ratio. Return-on-equity measures profitability relative to shareholders' equity. Debt-to-net-income is not the standard ratio used to evaluate capital structure. In CSC company analysis, debt-to-equity is the direct measure of how a company is financed between debt and equity.