The terrestrial planets have a. relatively high densities. b. ...

[LCritchfi]

The terrestrial planets have
 a. relatively high densities.
  b. solid surfaces.
  c. weak magnetic fields.
  d. all of these.

Question 2

The Doppler effect is observed only when
 a. the source of a wave moves toward a stationary observer.
  b. there is relative motion between the source of a wave and an observer.
  c. an observer moves toward the stationary source of a wave.
  d. both the source of a wave and an observer are moving toward each other.

[jojobee318]

Answer to Question 1

d

Answer to Question 2

b

[LCritchfi]

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[jojobee318]

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