State two indicators of development and for each one explain how it can be used to assess the level of development of a country

The answer is c, i, iii, and iv. this is because farming and mining deal with harvesting raw materials, construction work falls under manufacturing, and piloting a plane is a service. ii is wrong because making bread is using  raw materials to produce goods, which would fall under the secondary sector, not primary.

Answergranite

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.)