Final answer:
The best revision is 'I began my presentation by showing how a solar cell and a wire could use the sun’s rays to make a fan spin.' which eliminates redundancy and focuses on the main components and purpose of the demonstration.
Step-by-step explanation:
The best revision of sentence 4, considering the goal to reduce wordiness and enhance clarity, is: "I began my presentation by showing how a solar cell and a wire could use the sun’s rays to make a fan spin." This revision eliminates redundancy and unnecessary details, focusing on the essential components of the demonstration and the purpose behind it. By simplifying the sentence, the clarity is improved, and the audience can easily grasp the connection between the solar cell, the sun's rays, and the resulting action of the fan spinning. Moreover, this clear and concise starting point sets the stage for the rest of the presentation, drawing the audience into the topic of conservation and the innovative use of solar energy.