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What do the digestive and excretory systems have in common?
Both break down food.
Both produce urine.
Both get rid of waste material.
Both filter out waste material.

What were the main components of earth’s earliest atmosphere? oxygen and ammonia hydrogen and helium oxygen and nitrogen hydrogen and nitrogen

Which of these statements is false? a. others may notice a problem with a relationship before the people involved. b. the first sign of a problem with a relationship is a feeling of anger. c. damaged relationships can be repaired. d. even good relationships can be damaged.

Is there any solid scientific evidence that humans have been cloned?