Indicate Which of the Following Is Least Important in Doing $\lambda$

Multiple Choice

Indicate which of the following is least important in doing a complementation test with coinfection of phage T4.

A) ensuring that sufficient phage of both strains are present
B) recovering phage from the plaques after growth and lysis
C) counting the plaques that are produced on
D) control using both mutations in cis configuration and a wild type
E) coli K( $\lambda$ )