Reactivating deals that were put on hold may be unwise in some industries where fundamental changes during the crisis have weakened the competitive position of deal targets or hurt the structural attractiveness of their markets
A.
where fundamental changes during the crisis have weakened the competitive position of deal targets or
B. in which fundamental changes during the crisis
has weakened the competitive position of deal targets and
C.
where fundamental changes during the crisis have weakened the competitive position of deal targets and
D. in which fundamental changes during the crisis have weakened the competitive position of deal targets or
E.
where fundamental changes during the time of the crisis have weakened the competitive position of targets of the deal and
On GMAT, where is used for Places only. Since industries are not places, where usage is incorrect.
Fundamental changes are plural, hence it must use "have".