The Number of Technological Civilizations in Our Galaxy Is Limited

question 43

Multiple Choice

The number of technological civilizations in our galaxy is limited by

• A) the number of stars in our galaxy.
• B) the fraction of stars with planets.
• C) the number of planets per star in habitable zones longer than a few billion years.
• D) the fraction of suitable planets where technical life forms evolve.
• E) all of the above.

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Definitions:

Sporophyte Generation

The diploid, spore-producing phase in the life cycle of plants that undergo alternation of generations.

Vascular Tissue

Specialized tissue in plants responsible for water and nutrient transport throughout the organism.

Megaspore

One of the two types of spores produced by seed plants; develops into a female gametophyte (embryo sac).

Female Gametophyte

The haploid phase in the life cycle of plants and algae that produces female gametes or eggs.