In nebular theory how is some chemical similarity between the Sun and planets explained?

Correct answer: They formed from common solar nebula material

Direct answer: Option A, they formed from common solar-nebula material. Nebular theory says that the Sun and planets developed from one large, rotating cloud of gas and dust called the solar nebula. As gravity pulled this material inward, the central part became the young Sun, while material in the surrounding disk clumped together and formed planetesimals and then planets. Since the Sun and planets came from the same original reservoir, they can show broad chemical similarities, even though their exact compositions differ because temperature, distance from the Sun, and later geological processes affected them. Option A is correct because a shared source naturally explains shared elements and some common chemical characteristics. Option B is wrong because Earth's rivers formed much later and cannot explain the origin of the Sun or all planets. Option C is wrong because the planets and Sun did not arrive from different galaxies in this theory; they formed within the same solar system. Option D is wrong because the Moon's surface is only a small later body and could not create the Sun and planets. Exam cue: common chemical similarity usually points to common origin in the solar nebula.