The specific reaction sequence image or text is missing from the input. However, analyzing the visible options using NCERT sources:

1. Option 1 ($HC \equiv C^- Na^+$): This is sodium ethynide. It is formed when ethyne reacts with sodium metal, demonstrating the acidic nature of terminal alkynes due to the $sp$ hybridization of the carbon atoms [1], [2].
2. Option 4 ($C_4H_{10}$): This is butane. It can be prepared by the Wurtz reaction (treatment of ethyl bromide with sodium in dry ether) [3] or by the catalytic hydrogenation of butene/butyne [4], [5].

Since the provided 'Probable Answer' is Option 2, and the sequence typically leading to butane (Option 4) in NEET exams involves Wurtz reaction or reduction, there is a mismatch or missing information preventing definitive verification. The acidic character of alkynes and preparation of alkanes are key concepts likely tested here.