Internal Audit Services

You are separately considering Plant Co’s request to provide internal audit services and the remit of these services if they are accepted.
Which of the following would result in Horti & Co assuming a management responsibility in relation to the internal audit services?

(1) Taking responsibility for designing and maintaining internal control systems
(2) Determining which recommendations should take priority and be implemented
(3) Determining the reliance which can be placed on the work of internal audit for the external audit
(4) Setting the scope of the internal audit work to be carried out
A 1 and 3
B 2, 3 and 4
C 1, 2 and 4
D 3 and 4 only

Correct answer is C.
Isn’t the IA responsible for testing the effectiveness of internal controls, then why would it be responsible for designing and maintaining them?
Please let me know! Thank you in advance!