Why Did the Presence of Cyanobacteria on Earth in the Past

question 8

Multiple Choice

Why did the presence of cyanobacteria on Earth in the past allow humans to exist?

• A) It was the first form of life.
• B) It oxygenated the atmosphere.
• C) It fertilized the soil to let plants grow.
• D) It increased the carbon dioxide in the atmosphere, causing the greenhouse effect.
• E) It was the first life form based on DNA.

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Definitions:

Ductal Carcinoma

A type of breast cancer that begins in the cells of the ducts.

Carcinoma

A type of cancer that begins in the skin or in tissues that line or cover internal organs.

Ductal

Pertaining to or involving ducts in the body, such as those in the glands, pancreas, or mammary glands.

Leukemias

A group of cancers that affect the blood and bone marrow, characterized by an overproduction of abnormal white blood cells.