Which statement describes decision coverage accurately?

Decision coverage is fundamentally concerned with the outcomes of conditional statements within the code, particularly focusing on ensuring that all possible outcomes of these conditions are tested. When we refer to decision coverage, we specifically mean assessing whether tests have adequately exercised all the decisions, such as 'if' statements and corresponding true and false outcomes.

The correct answer accurately reflects this concept, highlighting that it measures the proportion of decision outcomes exercised by tests. This means that each decision point in the software should be tested such that both the true and false paths of these conditions are executed at least once, ensuring a thorough examination of the logical decisions made by the code. This thoroughness helps uncover potential defects that may arise from these different pathways.

In contrast, other options refer to aspects like paths through the code or business flows, which are more pertinent to other forms of coverage, such as path or business process coverage, rather than directly addressing the specifics of decision outcomes. Hence, option D stands out for accurately representing the focus of decision coverage in testing contexts.