Astronomers have developed several ways to measure the vast distances between Earth and the stars and galaxies. What do you know about two of these techniques?
An astronomical unit (A. U.) is the average distance between the Earth and the Sun.
Our galaxy, the Milky Way, is about 150 light-years across
An astronomical unit is about 93 million kilometers.
Astronomers measure distances to objects which are outside our solar system in light-years.
The A. U. is used to measure distance within our solar system.
A light-year (ly) is the distance that light can travel in one year in a vacuum.

Explanation:

Astronomers estimate the distance of nearby objects in space by using a method called stellar parallax, trigonometric parallax

Hope it Helps

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.