Incident commanders within the unified command do all of the following, except:
a. communicate to make joint decisions and speak as one voice.
b. concur on the selection of the general staff section chiefs.
c. work together to establish resource ordering procedures.
d. form multiple command structures if disagreements arise

The answer is D. Form Multiple command Structures if disagreements arise.

Disagreements bound to happen in every organizations. Creating multiple command structures everytime disagreement arise will simply make it worse.

Usually, if a disagreement arise, the commanders will discuss the problem throughly find the solutions together