Psychologist: Research has shown that a weakened immune system increases vulnerability to cancer.
Conclusion
Cancer-patient support groups might have genuine therapeutic value
Evidence
Cancer-patient support groups reduce stress for their participants.
And a weakened immune system increases vulnerability to cancer.
Evaluate
Sorry, what? What is the argument? Sometimes LSAC throws us these convoluted messes where it's hard to process what the author is even trying to argue, let alone argue with him.
The good news is that when the logic is this hard to put together, it normally means that once you figure out the author's thought process, the correct answer is just testing the connective tissue you assembled.
Since our author's conclusion is saying cancer support groups —c→ therapeutic value we need to figure out how the author got from cancer support group to therapeutic value.
The evidence definitely talks about support groups (it says they reduce stress), but where does the therapeutic value come in?
Here we have to exert some will power / outside knowledge. The first sentence is talking about immune system and vulnerability to cancer. And the following sentence begins "So". That means the author thinks the first sentence is a reason we should believe that cancer-support groups have a therapeutic value (i.e. they help you with your cancer).
The author must be assuming that cancer-support groups have something to do with how strong or weak your immune system is, if the first sentence supposedly supports the conclusion.
Obviously, a weaker immune system wouldn't help your cancer, so the author must be thinking that cancer support groups lead to a strengthened immune system, which leads to decreased vulnerability to cancer.
How do cancer support groups lead to a strengthened immune system? We'll take the one thing the author told us about them (reduce stress) and assume the author is drawing some connection from stress to immune system.
It seems like this is the intended causal story the author is making.
Cancer Reduced Stronger Less vulnerable support → stress → Immune → to cancer groups
Goal
The link we invented there for the author was the middle one, so we should look for an answer saying that "reduced stress" can lead to "stronger immune system" or some other way of stating that those two are connected.