Engineers are building machinery to harness the power of ocean waves. As an abundant source of clean energy, wave power can be categorised along with (8) ________ sustainable energy sources, such as wind and solar power.
Wave power is extracted by wave energy converters, or WECs, which are placed along ocean (9) ________ that produce strong waves. The first wave farm, (10) ________ comprises three WECs, was built off the coast of Portugal in 2008. It was set to produce over two megawatts of energy – enough to power 2,000 homes. Sadly, the project hit a (11) ________ block two months into operation and has remained offline ever since, demonstrating the high probability of technical difficulties that can still arise.
Engineers are continuing to build wave farms worldwide, (12) ________ it is worth cultivating the extraction of wave power. The amount of power that could potentially be extracted is three terawatts – enough for billions of homes and businesses.
(Adapted from "Use of English for advanced")