Which of the following are true about electricity and magnetism? i. an electric current can be produced by a changing magnetic force. ii. a magnetic force can be produced by an electric current. iii. energy cannot be transferred by an electric current. iv. a magnetic force can attract a metal object only if the object is touching the magnet.

I. An electric current can be produced by a changing magnetic force.

II. A magnetic force can be produced by an electric current.

they emit helium gas that attaches to nearby planets.

they remove low-mass elements from the planets’ crust.

they cause nuclear fusion inside the inner core of planets.

they produce heavy elements such as iron and gold.

explanation:

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.