(a)
Answer: opposition
The planet Venus can never reach  planetary
configuration when viewed from Earth is opposition.
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(b) Answer : weight
Mass is amount of matter contains in the objects. It is an
independent quantity. It does not depend on the gravity. That means
it does not vary from place to place.
Therefore, the mass is same either on earth or on Mars.
The weight is gravitaional pull acting on pbjects. The gravity
is different from one planet to other.Therefore, we observe
significant change in weight.
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accounted for the same observed motions of the planets as the
geocentric theory but did so in a much simpler way.
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