Final answer:
The Earth has experienced multiple ice ages in the past billion years or more. There have been at least four ice ages, with each ice age consisting of multiple glaciation periods when glaciers grew on land.
Step-by-step explanation:
The Earth has experienced multiple ice ages in the past billion years or more. Scientists have identified at least five significant periods of cooling on the planet, commonly known as ice ages. Each ice age included multiple glaciation periods when glaciers grew on land.
During these ice ages, which were primarily caused by changes in the tilt of Earth's rotational axis due to the gravitational effects of other planets, there were times when the entire ocean froze over, a situation called snowball Earth.
Therefore, the correct answer to your question is A) Four ice ages.