The main unit processes used for the production of hydrogen from natural gas are stream reforming $(\text{SR})$, pressure swing adsorption $(\text{PSA})$, low temperature water gas shift reaction$(\text{LT WGS})$ and high temperature water gas shift reaction$(\text{HT WGS})$. The correct sequence of these in the plant is

1. $\text{SR; LT WGS; HT WGS; PSA}$
2. $\text{PSA; SR; LT WGS; HT WGS}$
3. $\text{SR; HT WGS; LT WGS; PSA}$
4. $\text{PSA; HT WGS; LT WGS, SR}$