Answer:
Jobs argument
Step-by-step explanation:
-The national-security argument states that some industries have to be protected by imposing tariffs to maintain the local production in case of a war.
-The unfair-competition argument says that the domestic market has to be protected when there is unfair competition because companies from other countries are subject to different regulations.
-Using-protection-as-a-bargaining-chip argument states that the threat of imposing a restriction can help to eliminate a restriction that was imposed by another country.
-Infant-industry argument says that new industries have to be protected because they don't have economies of scales that their competitors from others countries have.
-The jobs argument claims that the trade with other countries eliminates the local jobs.
According to this, the answer is that the senator is using the jobs argument to argue for the trade restriction on steel rods because he claims that it is necessary to impose those restrictions to protect the workers from losing their jobs.