Stars which appear single to the naked eye but are double when seen through a telescope are A. novas and supernovas B. binaries C. asteroids D. quasars

novas and supernovas
binaries
asteroids
quasars

The correct answer is B. binaries.

A binary star system is a star system consisting of two stars that are gravitationally bound to each other. The stars orbit around a common center of mass, and the distance between the stars can vary widely. Some binary stars are so close together that they appear to be a single star to the naked eye, but can be resolved into two stars with a telescope. Other binary stars are much further apart, and can only be detected as binary stars through their orbital motion.

Novas and supernovas are types of stellar explosions. Novas are much less powerful than supernovas, and they do not destroy the star that undergoes the explosion. Supernovas are much more powerful than novas, and they can destroy the star that undergoes the explosion.

Asteroids are small, rocky bodies that orbit the Sun. They are much smaller than planets, and they do not have enough mass to form a spherical shape. Asteroids are found in the asteroid belt, which is located between the orbits of Mars and Jupiter.

Quasars are very distant, active galaxies. They are powered by supermassive black holes at the center of the galaxies. Quasars are extremely bright, and they can be seen from billions of light-years away.

In conclusion, the correct answer is B. binaries.