(a) The prefix di in tine IUPAC narne Indicates that two identical substituent groups are present in the parent chain. Since two methyl groups are present in the of the C-2 of the parent chain of the given compound, the correct IUPAC name of the given compound is 2,2-dimethylpentane.
(b) locant number 2, 4, 7 is lower than 2 , 5, 7 hence ,the IUPAC name of the given compound is 2,4,7-trimethyloctane.
(c) It the substituents are present in the equivalent position ot the parent chain, then the lower number is given to the one that comes first in the name according to the Alphabetical order. Hence, the correct IUPAC name of the given compound is 2-chIcro -4-methylpentane.
(d) Two functional groups — alcoholic and alkyne -are present in the given compound, The principal functional group is the alcoholic group. Hence, the parent chain will be suffixed with ol.The alkyne group is present in of the C-3 of the present chain . hence,the correct IUPAC name of the given compound is but But-3-yn-1-ol.