The 12th one

Dear Student,
The sample space for getting a total of 15 when a die is rolled three times is {(3,6,6),(4,5,6),(4,6,5),(5,5,5),(5,4,6),(5,4,6),(6,4,5)(6,5,4),(6,6,3),(6,3,6)}.
Out of all the possible chances in the sample space 4 occurs as the first number in two cases only.
Hence total number of outcomes is- 10
Possible/Favourable outcomes is -2
Probability of 4 being the first throw
$$\begin{gathered} \frac{Favourable outcomes}{Total no. of outcomes} \\ =\frac{2}{10}=\frac{1}{5} \end{gathered}$$
Option B

Hope this information has solved your queries.
Regards