¿Qué problemas surgieron después de la guerra y hubo que reconstruirlos?

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.

Most of the land is used for housing/commercial uses