What was the role of Earth's gravity in making the secondary atmosphere stable?

Correct answer: It held gases near Earth

The direct answer is A: Earth’s gravity held atmospheric gases near the planet and helped the secondary atmosphere remain stable. Gravity is the attractive force associated with mass. Earth has enough mass to pull gas molecules toward it, so gases do not simply escape into space. During the formation of the secondary atmosphere, volcanic activity released gases such as water vapour, carbon dioxide, and nitrogen. Gravity helped retain these gases around Earth, while cooling and other processes later shaped the atmosphere. The reasoning is: Earth has mass → mass produces gravity → gravity attracts gas molecules → gases remain around Earth → an atmosphere can be maintained. Option A is correct because it states this retaining function. Option B is wrong because gravity does not turn gases into stone; that would be a physical and chemical transformation unrelated to atmospheric retention. Option C is wrong because gravity did not turn oceans into fire. Option D is wrong because the Moon’s orbit is not the role being asked about, and gravity did not “stop” the Moon. Gravity cannot prevent every gas from escaping, especially very light gases, but it retained enough gas for an atmosphere. Memory cue: gravity is Earth’s invisible hold on the atmosphere.