This question's explanation and your answers so far.
ある機械の組立て作業のメンバになった P さんは，リーダの指導の下，作業工程を確認するためにアローダイアグラムを作成した。作成したアローダイアグラムは，効率よく作業を進行させるために，メンバ間で共有することにした。図 1 にアローダイアグラムを示す。 各工程は 1 人で行うものとして計画し，メンバの誰が担当しても予定日数で作業を終了するものとする。 アローダイアグラムを作成する手順の a に入れる記述として，適切なものはどれか。 〔手順〕組立て作業を構成する各工程に対して， a 順番を決め，アローダイアグラムを作成する。
Cost is a matter of budget management and cannot serve as the basis for deciding the order in which tasks are carried out. What an arrow diagram represents is the precedence relationships among tasks, not costs, so this is inappropriate.
正解 An arrow diagram (also called a PERT diagram) is a schedule-management technique that connects the dependency relationships between tasks with arrows, making the overall flow of the work and its required duration visible. To draw it, you must first clarify the precedence relationship — which task each process can be started after (the predecessor/successor relationship) — and then decide the order based on that. Therefore blank a should be filled with “by investigating the precedence relationships among the tasks”, and the correct answer is “イ”.
Risk is a matter of risk management and does not stipulate the order of which task should be carried out first. It is not the direct basis for creating an arrow diagram, so this is inappropriate.
The skills of the members in charge are a matter of staffing (resource) allocation, which is a separate issue from the precedence relationships of the tasks themselves. The order is determined by the dependency relationships among tasks, not by skills, so this is inappropriate.