This is an addition reaction with  being added to an alkene (ionic addition). To reach the correct answer first we need to add the  to one of the carbons by using electrons from the double bond. This next step is crucial because the positive charge (carbocation) that forms needs to be in the most substituted position. However, hydride shifts can occur moving a hydrogen atom over to an adjacent carbon to form the most stable carbocation. In this case, the positive charge on the secondary carbon adjacent to the tertiary carbon will first get the positive charge and then a hydride shift will occur amongst those two carbon leading to a more stable tertiary carbocation. Finally, the  will attack the carbocation from both sides, and then we will have an alkyl halide. The most stable intermediate (carbocation) produces the greatest quantity of the stable product. 

This is a classic acid catalyzed alkene reaction. Because of resonance, several reactions have multiple products.

2-Methyl-2-butene will react the fastest with hydrobromic acid because when it reacts, it will form the most stable carbocation among all of the alkenes listed. This stability allows for the reaction to proceed much quicker than other compounds, therefore it will react the fastest.

The ozonolysis of alkenes forms either ketones or aldehydes. Subsequent reagents can be added to produces alcohols and/or carboxylic acids. 

The reaction mechanism goes through a carbocation intermediate as follows:

Therefore the answer is the following carbocation intermediate:

Reactions that proceed by syn addition include hydrogenation, epoxidation, and hydroboration-oxidation. Reactions that proceed by anti addition include halogenation, halohydrin addition and epoxidation followed by ring opening. Syn addition occurs because reagents must approach from only one side of the double bond. 

The reaction given is called a Markovnikov's addition reaction. This is a regiospecific reaction because only one orientation of the reaction occurs. It is an electrophilic addition reaction that involves the reaction of a halogenic acid such as  or  with an alkene. The hydrogen bonds to the carbon with the less alkyl groups bonded to the organic compound and the halogen ion bonds to the carbon with more alkyl substituents. Therefore the answer is:

The reaction given is called a Markovnikov's addition reaction. This is a regiospecific reaction because only one orientation of the reaction occurs. It is an electrophilic addition reaction that involves the reaction of a halogenic acid such as  or  with an alkene. The hydrogen bonds to the carbon with the less alkyl groups bonded to the organic compound and the halogen ion bonds to the carbon with more alkyl substituents. Therefore the answer is:

Molecular chlorine reacts with an alkene in the presence of water to yield a halohydrin product. Below is the mechanism for this reaction:

Molecular bromine reacts with an alkene in the presence of water to yield a halohydrin product. Below is the mechanism for this reaction: