Which of the following reactions will yield 2,2-dibromopropane?

$\begin{array}{1 1}(a)\;CH_3-CH=CH_2+HBr\rightarrow \\(b)\;CH_3-C\equiv CH+2HBr\rightarrow \\(c)\;CH_3CH=CHBr+HBr\rightarrow \\(d)\;CH\equiv CH+2HBr\rightarrow \end{array}$