Step 1: Understanding the Concept:
Identifying standard English verb-noun collocations in decision-making contexts.
Step 2: Detailed Explanation:
The idiomatic collocation in problem-solving is 'to reach a decision' (meaning to make a formal judgment or choice after evaluating available evidence).
One does not 'reach a fact' or 'reach a development' in this grammatical structure.
Step 3: Final Answer:
Hence, 'Decision' appropriately completes the sentence.