Here's a bigger picture, Iran does not have the capability to shut down the straights only the major powers do.
OH GOOD LORD...you did NOT just type that...... (SIGH) Nope, you did!
Iran has a large number of fast attack small boats they can use to attack and stop vessels, to include oil tankers. they have coastal anti-shipping batteries that can strike vessels through the narrow straights. They have MINES they can use to close the straights, which they practice using quite often.
You really should educate yourself before you start making such STUPID.....sorry, 'uneducated'....remarks.