A. Where the problems arises is when we decide that we already know what it takes to do a job.

B. Where the problems arise is when we have decided we already know what it takes to do a job.

C. Where the problems arise is when we decide that we already know what it takes to do a job.

D. Where the problems arise is when we decide that we have already known what it takes to do a job.

A

B

C

D

C. C

In a takes into doing is awkward construction. In B have decided and already known D are incorrect.