Question

### Passage

Astrophysicists and astrobiologists simulated Martian surface environments to evaluate the survival and methane ($\text{CH}_4$) production of the methanogenic archaeon *Methanosarcina barkeri*. Under optimal laboratory conditions, *M. barkeri* is cultured anaerobically in a liquid medium under an atmosphere of $80\%\ \text{H}_2$ and $20\%\ \text{CO}_2$ at $37^\circ\text{C}$ (Standard Growth Condition).

In the Martian simulation experiments, the researchers varied three main environmental variables:
1. Atmosphere: Standard Growth atmosphere vs. Simulated Martian Atmosphere (SMA: $95.3\%\ \text{CO}_2$, $2.7\%\ \text{N}_2$, $1.6\%\ \text{Ar}$, and $0.13\%\ \text{O}_2$).
2. Substrate: No substrate (liquid medium only) vs. Inert quartz sand vs. Simulated Martian Regolith (SMR) containing $1.0\%\ \text{Mg(ClO}_4)_2$ (perchlorate salt, a strong oxidizing agent).
3. Radiation: Shielded (no UV exposure) vs. UV-irradiated (exposure to $200\text{--}400\text{ nm}$ UV flux).

To evaluate the specific effect of each environmental variable on the growth rate and $\text{CH}_4$ production of *M. barkeri*, the researchers prepared multiple experimental setups. To validate their conclusions, each test setup must be compared against a specific control or baseline setup that isolates the variable of interest.

Match each research goal with the appropriate control or baseline setup needed to isolate the variable of interest.