Final answer:
The Precambrian era featured the longest periods with no life forms on Earth.
Step-by-step explanation:
The correct answer is A. Precambrian. The Precambrian era is the longest period in Earth's history, lasting approximately 4 billion years. It is divided into three periods: the Hadean, Archean, and Proterozoic. During this era, Earth underwent significant geological and chemical changes, but it was only towards the end of the Precambrian that life started to emerge.
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