Problem:

Q: How is communication initiated and maintained with spacecraft?   A:
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A: radio waves


Problem:

Q: What is the process in which organisms reproduce sexually by joining gametes called?   A:
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A: fertilization


Problem:

Q: What keeps the moon orbiting earth?   A:
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A: gravity


Problem:

Q: Human mammary glands can produce what substance, which can be used to feed children?   A:
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A: