The reaction between which of the following reactants produces hydrogen?

Options

A. (a) `Zn + HCl`
B. (b) `BaO_(2) + HCl`
C. (c) `K_(2)S_(2)O_(8) + H_(2)O`
D. (d) `Na_(2)O_(2) + HCl`

Explanation

To determine which of the given reactants produces hydrogen gas, we need to analyze the reactions of each option with respect to the reactivity of metals and their ability to displace hydrogen from acids.

### Step-by-Step Solution:

1. **Identify the Reactants**: The question provides several reactants. We need to analyze each one to see if it can produce hydrogen gas when reacted with an acid.

2. **Understand the Reactivity Series**: The reactivity series of metals indicates that metals above hydrogen can displace hydrogen from acids. The relevant part of the series includes:
- Potassium (K)
...