Hmm seems odd that some were straightforward, then 1 was sooooo specific. Let's hope it is all reflected in the scaling of the options (even though Ag doesn't scale especially well).
I agree, 4 is C. And on the cytotoxic / killer thing: I have read about cytotoxic but my class Teacher always said "killer", as do some of my text books. So I got to the exam and thought "What's the difference?". Oh well, got it wrong I guess.
I felt the same way after Ag, then had Maths the day after.
I let myself have an hour or two feeling depressed, then had a big glass of water and went for a walk. After that I just knuckled down to getting ready for General Math.