What is the upper temperature range for stars?
a. 1,000,000 k
c. 40,000 k
b. 23,000 degrees c
d. 2,000,000 degrees c

Option (C)

Explanation:

The O stars are the hottest of all the stars which have a maximum temperature of approximately 40,000 K. They appear to be bluish in color. The hydrogen present on the surface of this type of stars are fully ionized, due to which it's surface temperature is extremely high. Some of the visible elements are also present such as oxygen, silicon, helium, and nitrogen.

These stars can survive for a period of nearly 10 billion years. These are the main sequence stars with high luminosity.

Thus, the correct answer is option (C).

answer called a epicycle;