An absentminded researcher follows the protocol described in Figure 14.7 and (at the end of the experiment)

Question:

An absentminded researcher follows the protocol described in Figure 14.7 and (at the end of the experiment) does not observe any yellow color in any of the tubes. Yikes! Which of the following mistakes could account for this observation?
A. Forgot to sonicate the cells
B. Forgot to add lactose to two of the tubes
C. Forgot to add 0-ONPG to the four tubes