CA A, a Chartered Accountant in practice, is considering the following professional assignments:

He is appointed as a receiver and agrees to charge fees at 4% of the realisation of assets.
He undertakes a debt-recovery assignment and agrees to charge 5% of the amount actually recovered.
He undertakes a mystery audit for a client and agrees that his remuneration will depend upon the number of operational lapses identified during the assignment.
He provides tax representation services to a non-audit client, which is not an associate concern, and agrees to charge 3% of the reduction in tax demand ultimately achieved by him.
He undertakes a cost-optimisation assignment and agrees to charge 10% of the benefit derived by the client.

Which ONE of the following correctly identifies the permissible arrangements?

A. 1, 2 and 5 only.

B. 1, 2, 3 and 5 only.

C. 2, 3, 4 and 5 only.

D. 1, 2, 4 and 5 only.