Directions: Read the following passage having some numbered blanks.

Oil is perhaps the most sought-after of all natural resources. However, a major difficulty in its (i) is that oil fields are very often found below the sea (ii). As a result, the search for oil is very expensive, and unless oil is found there in (iii) quantities the companies or governments involved are liable to lose heavily. Therefore, before (iv) starts, extensive surveys are carried out to see how much oil, or natural gas the rock formation is likely to yield. If the results are favourable, an oil rig is towed into position. The rig consists of a main scaffolding on which the men work and a derrick which supports the drill. This drill goes down thousands of feet until oil or a (v) of gas is reached. The next stage is to transport the gas or oil to the shore. In the case of gas, this is normally done by (vi) a pipeline below the sea, but oil, on reaching the top of the well, is more often transported in its (vii) state by ships. On shore it is (viii) into different fuels or it is (ix) chemically to turn it into a variety of (x) materials such as polythene.

Fill blank (x).