The United States has advocated strengthening oil embargoes against Iran because Iran is developing weapons-grade uranium. For the given question the correct option is the second option that is given. This kind of sanctions have been imposed against Iran several times and this has negatively impacted the economy of Iran in the long run. The main reason behind the recent sanctions against Iran is the fear that they would use this weapons-grade uranium to make nuclear missiles and bombs. These can at any period of time be used against United States and its allies.
