Central america serves as a(n) between north and south america
a. isthmus
b. canal
c. highland
d. plateau

None of them. they are likely to occur on any plate boundary

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.