Hi demk26 & j199393!
Demk26: Good diagramming! You are correct that answer choice (A) is a Supporter Assumption that is filling in the gap in the argument. But the gap here is a little more nuanced than you have diagrammed. As Brook described above, the gap is more so the jump from the premise that "some" of their predictions are wrong to the conclusion that they are not truly precognitive. Answer choice (A) provides us with that link between the premise and the conclusion because it states that:
Truly precognitive
ALL predictions accurate
Contrapositive:
ALL predictions accurate Truly precognitive
Some predictions do not come to pass =
ALL predictions accurate
Therefore, answer choice (A) fills in the gap between the premise and the conclusion.
J199393: You do not necessarily need to diagram the conditional reasoning present in this argument in order to find the gap in this argument. But understanding the conditional reasoning is important, especially in making sure that your answer choice links the terms in the right direction.
Hope this helps!
Best,
Kelsey