The nucleus of halley's comet is approximately a.16km by 8km b.1 meter wide c. 1km wide d.100km by 80km

It is A. 16km by 8km 

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.