When testing the effect of caffeine on cardiac rate, Valerie used water fleas as her test subject. She placed 5 water fleas ia beaker #1 with 50 mL normal water,
then placed 5 water fleas in beaker #2 with 1 mL coffee and 50 mL water, 5 water
fleas in a petri dish with 5 mL coffee and 50 mL water, and 5 water fleas 10 mL of
coffee and 50 mL of water. In the experiment above, what is the purpose of
beaker #1? *

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

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.