The universe began about 14 billion years ago and has been expanding and cooling ever since. What does this statement most completely describe? the Doppler effect
the big bang theory
cosmic background radiation
light years

b. the carbon cycle ensures living things have a source of hydrogen

both male and female gametes are produced by meiosis of the germ cells. therefore, both male and female gametes are haploid. one male and one female gamete unite during the fertilization to form the diploid zygote. in seed bearing plants, pollen grain is the male gametophyte, which produces sperm cells.

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