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[giveme170]

 Hana said she was not going to invite her brothers to her birthday party. However, among the gifts Hana received at her party was a recording in which she had expressed an interest. Since her brothers had planned to give her that recording, at least some of Hana's brothers must have been among the guests at Hana's Birthday party after all.

Reasoning error in the argument:

B) treats the fact that of someone's presence at a given event as a guarantee that that person had a legitimate reason to be at that event.

D) fails to establish that something true of some people is true of only those people

E) overlooks the possibility that a person's interest in one kind of thing is compatible with that person's interest in a different kind of thing.

Could someone break down the argument and explain what function each part of the argument plays? I think the CR would make much more sense to me if I understood the reasoning structure... Thanks for the help!

[Changed Name]

I don't know if this is the type of break-down you're looking for, but here goes nothing:

The argument here is claiming that at least some of Hana's brothers must have been at her party. Why? Because they planned on giving her some recording, and that was one of the gifts that she received at the party.

We are looking for a flaw. I think it's an obvious flaw in that it is more than possible that someone other than her brothers could give her that recording.

The tricky part is the way they phrase their answer choices.

I think the answer choice D best represents the flaw. "Fails to establish that something true of some people is true of only those people."

Something true of some people = her brothers planned to give her the record
True of only those people = only her brothers were going to give her this record

NOTE: if she did in the argument show that only her brothers would give her that record, then it would be a valid argument. But she never does express this.

[RiddledBasins]

You can also attack this as an assumption question.  There is a gap between the premises and the conclusion. 

Premises: Hana said she wouldn't invite her brothers.  Yet she got something she wanted anyway. 

Conclusion: Since her brothers had planned to give her what she wanted, Hana's brothers must have been among the guests at Hana's Birthday party after all.

You need something to link the two together.  What is she assuming that allows her to conclude that her brothers must've been at the party?  She's assuming that only her brothers could give her that present.  And this, without any further evidence, is flawed.

[carsonlions]

I also have a problem with this question, specifically answer B, which states "treats a fact of someone's presence at a given event as a guarantee that that person had a legitimate reason to be at that event"

So Hana's was going to invite her brothers, BUT what if they showed up anyway and gave her a recording?

It doesn't point out the flaw I guess, but it seems to connect with the loaded phrase, "Was not going to invite her brothers"

[MikePing]

The question does not forclose the possiblity that Hanna's brothers attended the event and gifted her the recording.  But, to say that one of the brothers "must" have been at the event, ignores the fact that someone else could have gifted her the recording--which is still a possibility given what we know. 

[jmorr9000]

Yeah, it's D because the fact that her brothers were going to give her the recording doesn't mean they were the only people who could.

No need to overthink this one.

[EarlCat]

You've got all kinds of general terms in these answer choices, purportedly describing the specific things from the argument.  So ask yourself which specific things those general terms are referring to.  Who is the someone?  What is the event?  What is the something? What is the one kind of thing and the different thing?  Then figure out which of these actually describes what happened in the argument.

[River]

Since her brothers had planned to give her that recording, Hana received at her party was a recording.
at least some of Hana's brothers must have been among the guests at Hana's Birthday party after all.

Here her bros planned to give her the recording This shows the mere intent of the bros to giver her the recording.  the fact that she received the recording does not necessarily evince their presence at the party but sffice only possibility of their attending party. Yet the conclusion says either of or some of the bros MUST have been present. The conclusion takes the mere possibility as a confirmatory truth.  Thus, the eror here is that the author conjectures her brothers were surely at her party only upon looking at the recording at her party. Can the presnece of the recording at her party convince you of their presnece?  Can thier plan to giver her the recording gurantee thier presence at her party?  Is it possible for somene else to giver her the recording?