Answer
a) ethane
b) $CH_3CH_2CH_2CH_2CH_3$
c) hexane
d) $CH_3CH_2CH_2CH_2CH_2CH_2CH_3$
Work Step by Step
a) 2 carbon atoms in the alkane. So, its name is ethane
b) pentane has 5 carbon atoms and 12 hydrogen atoms. Its formula is $CH_3CH_2CH_2CH_2CH_3$
c) 6 carbon atoms in the alkane. So, its name is hexane
d) heptane has 7 carbon atoms and 16 hydrogen atoms. Its formula is $CH_3CH_2CH_2CH_2CH_2CH_2CH_3$