When Estimating the Number of Technologically Advanced Civilizations in Our

question 21

Multiple Choice

When estimating the number of technologically advanced civilizations in our Galaxy,it is useful to consider

• A) the average life span of an alien.
• B) the average life span of the civilization.
• C) the distance to the civilization's planet.
• D) the type of advanced communication they use.

---

Definitions:

Cancer

is a disease characterized by the uncontrolled division of abnormal cells in a part of the body, leading to tumor growth and potential spread to other parts.

Memory Cells

Immune cells that remember past infections and can quickly respond to subsequent exposures to the same pathogen.

Antigen

A substance that, when introduced into the body, causes an immune response, often involving the production of antibodies.

Lymphocytes

Granular leukocytes formed in lymphoid tissue. Lymphocytes are generally small. See T Lymphocyte and B Lymphocyte.