第だい一いち選せん択たく

noun

first choice; primary option

Used in contexts like medical treatment, decision-making, or product selection to indicate the most preferred option.

• この薬くすりはインフルエンザの第だい一いち選せん択たく薬やくです。

  This drug is the first-line treatment for influenza.

• 彼かれの第だい一いち選せん択たくは海かい外がい