$CO_2$ gas is found in which of the following pairs of planets?

Asteroids are

Which of the following is the coldest planet?

The farthest objects in our Universe discovered by modern astronomers are so distant that light emitted by them takes billions of years to reach the Earth. These objects (known as quasars) have many puzzling features,which have not yet been satisfactorily explained. What is the distance in $km$ of a quasar from which light takes $3.0$ billion years to reach us?

Suppose the Sun was located at the position occupied by the nearest star,say,Alpha Centauri,$4$ light-years away. By what factor would the solar radiation received per second per unit area decrease?

Which one of the following planets has the longest day?