When Did the Level of Oxygen in Earth's Atmosphere Become

question 3

Multiple Choice

When did the level of oxygen in Earth's atmosphere become high enough to sustain aerobic respiration?

• A)1.0 billion years ago
• B)3.5 billion years ago
• C)1.5 billion years ago
• D)2.7 billion years ago

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Definitions:

Literacy Rates

The percentage of people who are able to read and write within a specific population.

Unemployment

The condition of being without a paid job despite actively looking for work, often measured by the unemployment rate which is the percentage of the labor force that is jobless.

Incomes

The income generated, particularly through regular payments, from employment or investment returns.

Environmental Quality

The condition or state of the environment based on various indicators, such as air and water purity, and the presence of healthy ecosystems.