According to the presentation, why does a gap between supply and demand open at sunset?
Listen to an Oral Presentation · ELPAC Grades 9–10 listening. The correct answer, and the reasoning behind it.
A presentation on an academic topic, followed by three or four questions.
Listen to the student presentation. Then answer the questions.
Electricity at Sunset
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Good afternoon. My presentation is about why California asks people to shift electricity use toward the middle of the day.
Solar panels across the state produce the most power between about ten in the morning and three in the afternoon. During those hours there is often more power available than the state can use, and some of it is sold cheaply to other states.
The problem arrives at sunset. Solar output falls to nothing within about an hour, and that is the same hour when people come home, turn on lights, cook dinner and plug in their cars. Demand climbs at the exact moment supply drops.
To close that gap, the state depends on large batteries charged earlier in the day, and on prices that make electricity cost more between four and nine in the evening.
So the simplest thing a household can do is run the dishwasher and the laundry before four o'clock instead of after dinner.
The question
Choose the best answer.
According to the presentation, why does a gap between supply and demand open at sunset?
- Batteries stop working once the temperature falls in the evening.
- Other states stop sending electricity to California after dark.
- Solar output drops to nothing just as people get home and use more power.Correct answer
- Households run their dishwashers and laundry in the middle of the day.
Why “Solar output drops to nothing just as people get home and use more power.” is correct
This is a cause-and-effect detail question, and the cause has two halves that arrive in one sentence. The speaker says solar output falls to nothing within about an hour, and that the same hour is when people come home and switch things on, then sums it up as demand climbing while supply drops. Students who hear only one half of the sentence tend to choose an answer about batteries or about other states.
Why the other answers are wrong
- Batteries stop working once the temperature falls in the evening. — Batteries are named as part of the solution; nothing is said about temperature affecting them.
- Other states stop sending electricity to California after dark. — Electricity is sold to other states at midday, and the talk never describes power coming the other way.
- Households run their dishwashers and laundry in the middle of the day. — Running appliances at midday is the speaker's recommendation for avoiding the gap, not its cause.
Practice more of this
More listening practice for Grades 9–10, or see the ELPAC practice test for grades 9–10. For other grades, see free ELPAC practice tests by grade.
This is an independent study resource. It is not affiliated with, endorsed by, or connected to the California Department of Education or the official ELPAC program. All questions here are original practice material written to match the published task formats.