The Exploratory Life-Sciences Experiments on Board the Viking Landers Spacecraft

The exploratory life-sciences experiments on board the Viking Landers spacecraft found evidence

A) of reactive chemistry in the Martian surface rocks,but no evidence of life or remnants of life forms.
B) of a sterile environment in which life could not have existed,probably sterilized by intense solar UV radiation,and a chemically inert soil,reacting with almost no reagents.
C) of primitive life forms such as elementary bacteria,which should not be a hazard when humans explore Mars.
D) that primitive life forms had existed on Mars earlier in its history,but they did not survive.