What factors may have caused the temperature variations in a classroom

Answercompass direction;

Just do the math, then think

Ascenario that doesnt  include any modern objects like electricity

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.