The correct answer is option 3: Tropopause.

Jet streams are strong and narrow air currents that flow in the upper levels of the atmosphere. They are usually found in the Tropopause, which is the boundary between the troposphere and the stratosphere. The troposphere is the lowest layer of the atmosphere, where weather events occur, and the stratosphere is the layer above it.

Option 1, Ozonosphere, is incorrect. The ozonosphere is another name for the ozone layer, which is located in the stratosphere but not specifically associated with jet streams.

Option 2, Mesosphere, is also incorrect. The mesosphere is the layer above the stratosphere, and jet streams are not typically found in this region.

Option 4, Ionosphere, is incorrect as well. The ionosphere is a region in the upper atmosphere containing a high concentration of ions and is not the location where jet streams are commonly found.

In summary, the correct answer is option 3: Tropopause, as jet streams are usually found in the boundary between the troposphere and the stratosphere.