doctors tetsimony

17. A patient accusing a doctor of malpractice will find it difficult to prove damage if there is a lack of some other doctor to testify about proper medical procedures.
(A) if there is a lack of some other doctor to testify
(B) unless there will be another doctor to testify
(C) without another doctor’s testimony
(D) should there be no testimony from some other doctor
(E) lacking another doctor to testify


OA :

C

but shouldn't it be A because A doesn't have the appostrophy which is less prefferd by gmat and also
it has the than ... if construction??

plzz help