1.  What is the first thing you are going to do with your cultures?
A.  Perform a Gram stain.

Not in this exercise, since you have a pre-made mixture of pure cultures.  Also, it is rare that a gram stain of a patient sample will tell you much, especially if you expect to see lots of other stuff like normal flora.  There are some cases where a Gram stain is useful - normally clean and sterile sites - such cerbrospinal fluid (CSF) for making a rapid presumptive diagnosis for meningitis.

However, all that being said, as you will see soon in the course, performing a Gram stain on a sputum sample is valuable since you might be able to see specific bacterial cell types and, more important, you will see the types of patient cells are in the sample.  As noted above, there are no human cells in the cultures for the lab.