The answer is E.
Following the destruction of the space shuttle Challenger, investigators concluded that many key people employed by the National Aeronautics and Space Administration and its contractors work an excessive amount of overtime that has the potential of causing errors in judgment.
(A) overtime that has the potential of causing
(B) overtime that has the potential to cause
(C) overtime that potentially can cause
These alter the meaning, they mean : "Overtime" causes an error in judgment. But its the practice - " key people employed by the National Aeronautics and Space Administration and its contractors work an excessive amount of overtime " that causes an error.
Now looking at :
(D) overtime, a practice that has the potential for causing
(E) overtime, a practice that can, potentially, cause
(D) is wordy and awkward.
Hence (E)
