Coronary angioplasty, part of CAD’s treatment involves:

The correct option is: Inflation of a tiny balloon inside an artery.

Explanation:
Coronary artery disease (CAD) occurs when the blood vessels that supply blood to the heart muscle become hardened and narrowed due to the buildup of cholesterol plaques. Coronary angioplasty, also known as percutaneous coronary intervention (PCI), is a minimally invasive medical procedure used to open these clogged heart arteries.

During the procedure, a thin, flexible tube called a catheter is inserted through a blood vessel in the arm or groin and guided to the blocked coronary artery. At the tip of this catheter is a tiny, deflated balloon. Once the catheter is positioned at the site of the blockage, the balloon is inflated. The inflation of the balloon presses the plaque buildup against the artery walls, effectively widening the passageway and restoring proper blood flow to the heart muscle. Often, a small wire mesh tube called a stent is left in place to keep the artery propped open permanently.

Let's look at why the other options are incorrect:
- "A new part of artery replaces the blocked section" describes coronary artery bypass grafting (CABG), which is a major surgical procedure rather than angioplasty.
- "To expand artery, medication is used" is incorrect because while medications (like vasodilators) can relax blood vessels, they do not physically clear or mechanically expand localized plaque blockages in the way angioplasty does.