Final answer:
All listed options regarding the interactions of complement receptor proteins with complement components are correct. Hence, 'None of the above' is the incorrect option to the question posed. (Option D).
Step-by-step explanation:
The student's question is about the complement receptor proteins and their specific interactions with components of the complement system.
In the given question, option a. CR1 recognizes C3b is correct, as CR1 is known to bind C3b. Option b. CR2 recognizes C3d is also correct because CR2 indeed binds to C3d.
The option c. CR3 recognizes iC3b is correct because CR3 is known to bind to inactivated C3b, often denoted as iC3b.
Therefore, the answer to the question 'Which of the following is incorrect?' would be d. None of the above, as all the listed interactions are correct.