Insert the missing words:

Some internal audit shops are turning towards a partnering arrangement, where they use parts of an external firm’s expertise to fill in the gaps between strategic requirements and current capacity. This ‘ . . . . . . . . . . . . . . . . . . . . . . ’ model has various positives as well as various negatives.

a. sharing and caring

b. outsourcing

c. co-sourcing

d. contracting-out