You are performing a Gram stain on an unknown bacterium.  You proudly show your pink bacilli to your facilitator who sadly shakes her head and says they should have been purple.  Which one of the following is the best explanation for where you went wrong?

A.   You forgot to add the carbol fuschin

B.   You forgot to add the iodine

C.   You skipped the alcohol decolourisation step

D.   You didn’t fix your cells to the slide before staining

(i)   Which response (A-D) is the best choice? (1 mark)

(ii)  Briefly explain your reasoning for your choice (2 marks)