Sentence Correction

With health care costs climbing even higher during this enrolment season, more
employers are adopting a tiered system for passing on the bulk of these costs to
their employees by assigning bigger contributions to workers in top salary brackets
and to offer some relief to workers who make less money.

A. for passing on the bulk of these costs to their employees by assigning bigger
contributions to workers in top salary brackets and to offer some relief to
workers
B. to pass on the bulk of these costs to its employees by assigning bigger
contributions to workers in top salary brackets and by offering some relief to
workers
C. for passing on the bulk of these costs to their employees through assigning
bigger contributions for workers in top salary brackets but offering some relief
to workers
D. to pass on the bulk of these costs to their employees by assigning bigger
contributions to workers in top salary brackets and offering some relief to
workers
E. to pass on the bulk of this costs to their employees by assigning bigger
contributions to workers in top salary brackets and by offering some relief to
workers

D[/spoiler]

D should be the answer as

A & C are out because the correct idiom is "adopt to"
B - use of "its" is wrong because "employers" is plural
E - use of "this costs" is wrong