2
QuizMultiple Choice

Unit Test — Unit test

Question 2 • 3262 CR Physics B 25/26

Which best describes the present-day universe?

Answer
A
opaque, expanding very slowly, stars produce heavy elements
B
transparent, expanding at an accelerated rate, stars produce heavy elements
C
opaque, expanding at an accelerated rate, stars produce only hydrogen and helium
D
transparent, expanding very slowly, stars produce only hydrogen and helium

Explanation

The present-day universe is transparent because light can travel freely through space rather than being scattered by the dense early-universe plasma. Its expansion is accelerating, as observations show that distant galaxies are moving apart at an increasing rate. Stars also create heavier elements, such as carbon and iron, through nuclear fusion and stellar processes. Therefore, “transparent, expanding at an accelerated rate, stars produce heavy elements” is the best description.

AI-written and checked against the verified answer.

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