First heart sound is................. while second heart sound is............. .

Explanation

### Step-by-Step Solution:

1. **Identify the First Heart Sound**: The first heart sound is known as "lub" (or "love"). It is produced when the atrioventricular valves close.

2. **Understand the Atrioventricular Valves**: The atrioventricular valves consist of the tricuspid valve and the bicuspid (or mitral) valve.
- The tricuspid valve is located between the right atrium and the right ventricle.
- The bicuspid valve is located between the left atrium and the left ventricle.

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