Final answer:
The statement is false; the anvil top of a thunderstorm is in the troposphere, not the stratosphere, typically extending up to the tropopause at about 12 km above Earth's surface.
Step-by-step explanation:
The statement that the anvil top of a thunderstorm often marks the beginning of the stratosphere is false. Atmospheric wind and weather, including thunderstorms, are confined to the lowest layer of the atmosphere, called the troposphere, which extends to about 12 km high.
The anvil top of a thunderstorm represents the point where the rising warm air of the thunderstorm meets the stable air of the tropopause, which is the boundary layer between the troposphere and the stratosphere. The stratosphere begins where the troposphere ends, and is typically cloud-free, extending to about 50 kilometers above the Earth's surface.