Liquid is filled in a flask up to a certain point. When the flask is heated, the level of the liquid

The correct option is: Initially falls and then rises

When a flask filled with a liquid is heated, the changes in the liquid level can be explained step-by-step through the process of thermal expansion:
1. Initial expansion of the flask: When heat is first applied to the flask, the flask container itself absorbs the heat before it reaches the liquid inside. As a result, the solid flask expands first, increasing its internal capacity. Because the liquid has not yet absorbed the heat, the level of the liquid initially falls to fill the newly increased volume of the flask.
2. Heat transfer to the liquid: Shortly after, heat conducts through the walls of the flask and is transferred to the liquid. Liquids generally have a much higher coefficient of volume expansion than solids:
${\gamma }_{\text{liquid}}>{\gamma }_{\text{solid}}$
3. Net rise in level: Because the liquid expands much more rapidly than the solid flask for the same temperature rise, the volume of the liquid increases significantly. This causes the liquid level to rise rapidly, surpassing its initial mark.

Therefore, the level of the liquid initially falls and then rises.