Question

question: why do mercury, venus, earth, and mars lack hydrogen and helium in their atmospheres? answer options: select one of four their gravitational pull is too strong. their masses are too large. their gravitational pull is too weak. they spin too quickly on their axes.

Explanation:

Hydrogen and helium are light gases. A planet's gravitational pull is needed to retain atmospheric gases. Mercury, Venus, Earth, and Mars have relatively weak gravitational pulls compared to gas giants. Weak gravity can't hold light gases like H and He, so they escape. The other options are incorrect: strong gravity would retain them, mass being large (these planets are smaller than gas giants) doesn't fit, and spin speed doesn't directly relate to retaining light gases.

Answer:

C. Their gravitational pull is too weak (assuming the options are labeled A - D as: A. Their gravitational pull is too strong, B. Their masses are too large, C. Their gravitational pull is too weak, D. They spin too quickly on their axes)