Given below are three statements (I -IV) regarding the human blood circulatory system .
(I) In the treatment of angina pectoris nitrous oxide and nitro glycerin are used.
(II) veins have thinner walls and broader lumen than arteries .
(III) Artificial pacemakers are used in arrhythmia.
How many of the above are correct statements ?

Options

A. I only
B. I , II and III
C. III only
D. I and II

Answer

To determine how many of the statements regarding the human blood circulatory system are correct, we will analyze each statement one by one.

### Step 1: Analyze Statement I
**Statement I:** "In the treatment of angina pectoris, nitrous oxide and nitroglycerin are used."

- **Explanation:** Angina pectoris is a condition characterized by chest pain due to reduced blood flow to the heart. Nitroglycerin is commonly used to treat angina as it acts as a vasodilator, widening blood vessels and improving blood flow. However, nitrous oxide is not typically used for this purpose. Therefore, while nitroglycerin is correct, the inclusion of nitrous oxide makes this statement partially incorrect.

**Conclusion:** Statement I is **incorrect**.

### Step 2: Analyze Statement II
**Statement II:** "Veins have thinner walls and broader lumen than arteries."

- **Explanation:** This statement is accurate. Veins do have thinner walls compared to arteries because they operate under lower pressure. Additionally, veins have a wider lumen (the internal space) than arteries, which allows them to hold more blood.

**Conclusion:** Statement II is **correct**.

### Step 3: Analyze Statement III
**Statement III:** "Artificial pacemakers are used in arrhythmia."

- **Explanation:** Arrhythmia refers to irregular heartbeats, and artificial pacemakers are devices implanted to help regulate the heartbeat by sending electrical impulses to the heart. This statement is true.

**Conclusion:** Statement III is **correct**.

### Final Conclusion
Now, let's summarize the correctness of each statement:
- Statement I: Incorrect
- Statement II: Correct
- Statement III: Correct

Thus, out of the three statements, **two statements (II and III) are correct**.

### Answer
The number of correct statements is **2**.

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