Travelers to Mars would have to endure low levels of gravity for long periods of time, avoid large doses of radiation, contend with the chemically reactive Martian soil, and perhaps even having to ward off contamination by Martian life-forms.

(A) contend with the chemically reactive Martian soil, and perhaps even having to ward
(B) contend with the chemically reactive Martian soil, and perhaps even warding
(C) contend with the chemically reactive Martian soil, and perhaps even ward
(D) contending with the chemically reactive Martian soil, and perhaps even to ward
(E) contending with the chemically reactive Martian soil, and perhaps even warding

How will I identify the best Option?

OA C