Ans: (D)
\(\mathrm{CH}_{3}-\mathrm{C} \equiv \mathrm{C}-\mathrm{H}\) is a terminal alkyne, which has acidic hydrogen.
\(\mathrm{CH}_{3}-\mathrm{C} \equiv \mathrm{C}-\mathrm{H}+\mathrm{CH}_{3} \mathrm{MgBr} \rightarrow \mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CMg} \mathrm{Br}+\mathrm{CH}_{4}\)