Add me too! I’m here for the summer and would love to join!

For the bacteria question, I don't know if it's a correct line of thinking (don't take my words as correct, just sharing my thoughts) but part of why I ruled out C alongside it simply not being the conclusion is that the question establishes that "in fact", "bacteria are extremely diverse", whilst the answer choice casts a bit of uncertainty through the "if". I felt as though the argument isn't based on a logical pattern of "if X then Y" and moreso "because X, then Y". Again, wasn't my primary way of confirming the answer but I found that it helped me eliminate it in comparison to B.