Even though K- and M-type stars are suitable for life, why might they not have many habitable planets around them?
A) because their habitable zones are very wide
B) because their habitable zones are very narrow
C) because their lifetimes are too short
D) because they contain too few heavy elements to form planets
B
You might also like to view...
The paths of the planets' orbits lie in all different directions in the sky.
Answer the following statement true (T) or false (F)
What is the main optical element of a refractor telescope?
A. lens. B. mirror. C. combination of many small plane mirrors. D. prism of glass.
What is the main constituent of the atmosphere of Venus?
A) Oxygen B) Nitrogen C) Hydrogen D) Carbon dioxide E) Sulfuric acid
Approximately what proportion of people in the United States believe we have been visited by extraterrestrials?
A) around 33% or a third B) about 50% or a half C) less than 1% D) more than 90%