Explanation:

When the stopcock between the two glass bulbs A and B is opened, the gas will flow from the higher pressure region (bulb A) to the lower pressure region (bulb B) until the pressure in both bulbs is equalized.

Initial Conditions:
- Volume of bulb A = 100 ml
- Volume of bulb B = 0 ml (empty)
- Pressure in bulb A = unknown
- Pressure in bulb B = unknown

Gas Law:
According to Boyle's Law, the pressure and volume of a gas are inversely proportional at constant temperature. Mathematically, it can be represented as: P1 * V1 = P2 * V2, where P1 and V1 are the initial pressure and volume, and P2 and V2 are the final pressure and volume.

Process:
1. Initially, the gas is confined to bulb A. So, the initial pressure in bulb A is unknown.
2. When the stopcock is opened, the gas will start flowing from bulb A to bulb B.
3. As the gas flows into bulb B, its volume increases. Let's assume the final volume of bulb A is V1 and the final volume of bulb B is V2.
4. According to Boyle's Law, the product of initial pressure and volume should be equal to the product of final pressure and volume. Mathematically, we can write it as: P1 * 100 ml = P2 * V1 + P2 * V2.
5. Since bulb B was initially empty, its volume is 0 ml (V2 = 0 ml). Therefore, the equation becomes: P1 * 100 ml = P2 * V1 + P2 * 0 ml.
6. Simplifying the equation: P1 * 100 ml = P2 * V1.
7. Now, since the gas flows until the pressure in both bulbs is equalized, the final pressure in bulb A will be the same as the final pressure in bulb B. So, we can write it as: P1 = P2.
8. Substituting P1 = P2 in the equation, we get: P1 * 100 ml = P1 * V1.
9. Simplifying further: 100 ml = V1.
10. Hence, the final volume of bulb A will be 100 ml.
11. Since the initial volume of bulb A is 100 ml, and the final volume is also 100 ml, it means the gas completely flows out of bulb A.
12. Therefore, the pressure of the gas in bulb A will fall down to zero.

Conclusion:
On opening the stopcock, the pressure of the gas in bulb A will fall down to zero as the gas flows completely into bulb B.