Final answer:
If plasma is not passed in the process of conjugation, it likely indicates that the process was interrupted, which would prevent the DNA transfer necessary for conjugation to be successful.
Step-by-step explanation:
The correct answer is c. The cells failed to merge. During the process of conjugation, if the plasma is not passed to another cell, it suggests that there might have been an issue with the formation or stability of the cytoplasmic bridge used to transfer genetic material. The options provided hint at various stages where the process could go wrong, such as membrane rupture, DNA replication failure, merging cell failure, or an interruption in the process. However, given the information in the student's question and the flowchart provided, the best answer would be that the process was interrupted. This could occur due to mechanical disruption or other factors preventing the completion of DNA transfer through the conjugation tube.