In the above figure, if ab = cd, then

It's impossible to solve it without a picture of that figure. If it's triangle then it has two similar angles. And if it has 90 degree angle then it's easy to find the value of the last side.

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.