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


A. Mars would have to endure low levels of gravity for long periods of time, avoiding large doses of radiation, plus contending

B. Mars would have to endure low levels of gravity for long periods of time, avoid large doses of radiation, contend

C. Mars, having to endure low levels of gravity for long periods of time, would also have to avoid large doses of radiation, plus contending

D. Mars, having to endure low levels of gravity for long periods of time, avoid large doses of radiation, plus contend

E. Mars, who would have to endure low levels of gravity for long periods of time, avoid large doses of radiation, contend with

OA B

Source: Official Guide