Explanation

The most important condition for the appearance of life is water.

Water is crucial for life for several reasons.

1. Solvent Properties: It dissolves various molecules, allowing for the chemical reactions necessary for life.
2. Chemical Reactions: It involves many biochemical processes, including metabolism and energy production.
3. Stability and Environment: It provides a stable environment for complex organic molecules to form and interact.

Life can exist without oxygen, as evidenced by anaerobic organisms that thrive in oxygen-free environments.

However, no known life form can exist without water.