Which of the following best describes steps that take place during a humoral immune response? a. t cells divide into t cells and cytotoxic t cells to fight infectious agents. b. cytotoxic t cells destroy pathogens that are detected by memory t cells. c. memory b cells divide and produce plasma cells that engulf and destroy pathogens. d. b cells bind to an antigen and produce plasma cells and memory b cells.

This picture represents humoral immunity, please read through it, and if you dont understand which option is your answer then i would recommend you read more about this topic, if you want it to be done fast, you can read this http://www.s-cool.co.uk/a-level/biology/immunity/revise-it/the-third-line-of-defence 
I hope you can come up with the answer on your own as it will be a good thing for you in your future exams :) 
Surely i can help you if you dont understand something so just ask :D