2-Butene formula: H3C-CH=CH-CH3. It can be both cis or trans. As the question do not specify, I'll treat it as a racemate (mixture of both).
It is a symmetric molecule so when it reacts with HBr there will not be distinguishable Markovnikov addition
products. It will yield racemic 2-bromobutane as single product. 2-bromobutane is a chiral molecule. However, HBr addition is not anti- or syn-addition specific (it is mixed) and so no specific form (R or S) would be favored.
a) So, it is not regioselective.
b) It is not stereoselective.
c) It is not stereospecific.
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