In an experimental investigation, the group that is not manipulated by the researcher and is then compared to the experimental group is called the blank? group.

The correct answer is - the control group.

Explanation:

The control group is one of two groups that are present in any investigation or experiment which is not getting any treatment as the experimental group gets. It remains constant or in natural conditions instead of influenced by any treatment or factor.

An experimanetal group that is manipulated by the researcher by the independent variable is compared to The control group to see the differences developed by the manipulation or influence.

that's what i got you can count the number of atoms

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.