3. Was pushed into the stratosphere
Most debris from atmospheric tests of nuclear weapons was pushed into the stratosphere.
Explanation:
Some of the radioactive debris from atmospheric nuclear weapon test lands relatively close. Some stays in the troposphere and are carried by air around the globe, lasting for about a month.
Most debris is pumped into the stratosphere, the next layer of atmosphere (from 5 to 50 km above) where it stays for months, and where it slowly drops backs to the earth.