The Sun and other stars are powered by nuclear fusion reactions, in which two atoms collide to form a single

Question

The Sun and other stars are powered by nuclear fusion reactions, in which two atoms collide to form a single heavier atom, releasing energy. Scientists have long believed that fusion has the potential to meet humanity’s clean energy needs. blank prior to December 2022, no fusion reaction in a laboratory setting had ever generated a net energy gain.

Which choice completes the text with the most logical transition?

Accepted Answer

Choice D is the best answer. Scientists believe in fusion&rsquo;s potential as an energy source, but have struggled to actually make it work-in other words, there is a contradiction between scientists&rsquo; beliefs and their reality. &ldquo;That said&rdquo; is a disagreement transition that works perfectly in this context. Choice A is incorrect. This choice uses a cause-and-effect transition, which doesn&rsquo;t make sense here. Scientists not being able to generate extra energy from lab fusion reactions isn&rsquo;t an effect of them believing in fusion&rsquo;s potential. Choice B is incorrect. This transition indies the addition of another supporting point. But this sentence is not adding a supporting point to the previous sentence-scientists not being able to successfully generate energy from fusion isn&rsquo;t another point in favor of fusion meeting humanity&rsquo;s clean energy needs. Choice C is incorrect. This choice uses a transition that introduces or elaborates on a particular example. But this sentence doesn&rsquo;t give an example of scientists&rsquo; belief in fusion&rsquo;s potential to meet humanity&rsquo;s clean energy needs-in fact, it contrasts that optimistic belief with the reality of past failures to successfully employ fusion for energy production.

Question 305de7