Read the following passage about the importance of renewable energy and mark the letter A, B, C, or D on your answer sheet to indicate the option that best fits each of the numbered blanks from 18 to 22.

As the world faces increasing environmental challenges, the shift towards renewable energy sources has become more critical. Solar and wind energy (18) ______. This transition is vital for reducing carbon emissions and combating climate change. Many countries have invested heavily in these technologies (19) ______, allowing for sustainable energy solutions.

Governments around the world have implemented policies that encourage the use of renewable resources. For instance, incentives are (20) ______ to promote solar energy installations in residential areas. However, the impact of these policies is often debated. Some critics argue that (21) ______, and that relying solely on renewable sources can be impractical in the short term.

Despite the challenges, the future of renewable energy looks promising. Innovations continue to (22) ______, leading to more efficient technologies that can support a sustainable energy future.