What does the phrase gravitational pull mean as it is used in the text? Because meteors are so small, they often get pulled into planetary orbits, while asteroids and comets are large enough that they stay within the gravitational pull of the sun.

1. A force that pushes one thing away from another
2. Something that makes an object stay on the ground
3. Something that pulls an object strongly downward
4. The force of one thing pulling another thing closer

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.