The correct answer is option 4: Release of carbon dioxide gas.

When yeast is added to dough, it undergoes a process called fermentation. During fermentation, the yeast consumes the sugars in the dough and converts them into carbon dioxide gas and alcohol. The carbon dioxide gas is responsible for the rising of the dough.

Option 1, an increase in temperature, is not the direct cause of the dough rising. While it is true that yeast activates and ferments more rapidly at higher temperatures, it is the carbon dioxide gas that causes the dough to rise.

Option 2, an increase in the amount of the substance, is not the cause of the dough rising. Adding more dough mixture may result in a larger volume of the risen dough, but it is not the reason why the dough rises.

Option 3, an increase in the number of yeast cells, plays a part in the fermentation process but is not the direct cause of the dough rising. It is the carbon dioxide gas produced by the yeast cells that actually causes the dough to expand.

Therefore, option 4, the release of carbon dioxide gas, is the correct answer.