Which statement is true about all of the countries in Mainland Southeast
Asia?
A. They are all small.
B. They are all under the rule of China.
C. They are all wealthy.

"pacesetter of the south," comma inside the quotes

It's between the sagittarius and perseus arms of the milky way.

Airplanes usually fly in the lower part of the stratosphere - there is nearly no water vapor and it's very dry, so it to avoid big turbulences. it's about 8-10 kilometers above ground (depending on weather conditions, region etc.)