The BEST Estimate for the Time of Production of Most

question 72

Multiple Choice

The BEST estimate for the time of production of most craters on both Mercury and the Moon is

• A) relatively recently, about 4 billion years after planet formation.
• B) in the first 800 million years after planet formation.
• C) about halfway through their lives, or about 2.3 billion years after planet formation.
• D) at a relatively constant rate throughout their lives, up to and including the present day.

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Definitions:

Reflexes

Involuntary and nearly instantaneous movements in response to stimuli, as part of the body's protective mechanism.

Medulla Oblongata

The lowest section of the brainstem, controlling autonomic functions such as breathing and heart rate.

Sneezing

Sneezing is a reflex action to expel air forcefully from the nose and mouth to clear the nasal passages.

Spinal Reflex

An involuntary and nearly instantaneous movement in response to a stimulus, mediated by the spinal cord.