Hi, 
It looks like you are doing it right! Try typing in the "Please pick a subject: " area "es" or "pt" or pretty much any subject then press Enter. If that didn't work let me know. 
Bristlefrost

Also be sure you convert subject to lower case letters using the function subject = subject.lower(). 

Lastly, try putting the input line in a while loop like this:

subject = ""

subjects = ["math", "science", "computing", "humanities"]

while subject not in subjects:

     subject  = ("Please pick a subject (math, science, computing, or humanities)? ")

     subject = subject.lower()

Now the user must choose a subject that is in the list subjects and it converts to input to all lowercase letters