In the following passage, some words have been left out. Read the passage carefully and select the correct answer for the blank. However, with rapid progress in technology in other _____ energy sources such as wind and solar power, the collapse of oil prices and the expansion in gas projects as a viable and clean alternative, that promise has changed.

Introduction / Context:
This cloze question belongs to a passage about energy choices. The sentence focuses on energy sources such as wind and solar power, which are well known in environmental discussions. The blank requires an adjective that correctly describes the type of energy these sources represent in modern energy policy language. Knowing basic environmental vocabulary is crucial here.

Given Data / Assumptions:

• Sentence fragment: progress in technology in other _____ energy sources such as wind and solar power.
• Examples given: wind power and solar power.
• Options: brief, renewable, untenable, temporary.
• The passage discusses non fossil options and clean alternatives.

Concept / Approach:
Wind and solar power are classic examples of renewable energy sources because they rely on natural processes that are constantly replenished. The adjective renewable has a very strong and specific connection with these examples. The other adjectives do not describe energy types and do not match the positive environmental context. Therefore, recognising that wind and solar form the standard pair with renewable is the key to answering this question correctly.

Step-by-Step Solution:
Step 1: Identify the category of energy under discussion: wind and solar power.Step 2: Recall that these are almost always referred to as renewable energy sources in media, policy and academic texts.Step 3: Test renewable in the sentence: progress in technology in other renewable energy sources such as wind and solar power.Step 4: Notice that this matches standard phrases like renewable energy technology and renewable energy sector.Step 5: Check other adjectives, and see that brief, untenable and temporary do not describe the inherent nature of wind and solar energy.Step 6: Choose renewable as the only accurate and context appropriate option.

Verification / Alternative check:
Read the entire clause with the chosen word: with rapid progress in technology in other renewable energy sources such as wind and solar power. This is exactly how a newspaper article or policy report would phrase it. If we replaced renewable with temporary, we would be saying that wind and solar power are short lived, which is not true and completely breaks the logic of the passage. Using untenable would mean unsustainable or impossible to defend, which again contradicts the idea of these sources as clean alternatives.

Why Other Options Are Wrong:
Brief: This means short in duration and is generally used for time, not for types of energy. A brief energy source is not a standard expression. Renewable: This is the correct answer and describes energy that can be naturally replenished. Untenable: This means not able to be defended or maintained. Calling wind and solar untenable energy sources would be inconsistent with their role as promising clean alternatives. Temporary: This suggests something that exists only for a short time, which does not describe the inherent nature of wind and solar power as energy categories.

Common Pitfalls:
Some test takers may choose a word based only on its general positive or serious sounding nature, without checking whether it actually collocates with energy sources. Others may not know the specific environmental term renewable and try to guess. To avoid such errors, it is useful to build a small core vocabulary for common exam themes such as environment, economics and technology. Renewable energy is a must know phrase, and whenever you see wind and solar together, renewable should immediately come to mind.

Final Answer:
The correct adjective to complete the phrase is renewable, giving the expression renewable energy sources such as wind and solar power.