Advertisement: The world’s best guitars have solid tops made of spruce

E Weakens the conclusion, since one may buy a Classical guitar, and since Wender doesn't produce the best Classical guitar, one may not be buying the best guitar. Hence IMO E

You need to find the flaw in the argument here and not strengthen it.

Hence, I think E should be the answer.

It says one of the best not "the best".
I dont think E is relevant.
C tells us that Wender sells more guitars than does any other company.Hence the reason it buys more spruce wood than any other guitar company is simply because it has to produce more guitars than any other company.
C is the correct answer.

My analysis...

Structure
Conc: if you buy a Wender guitar, you are buying one of the best guitars available today.
P1: The world’s best guitars have solid tops made of spruce.
P2: Wender purchases more spruce wood than any other guitar company.

Pre-thinking
The author assumes that Wender will use the spruce wood it buys to make the solid tops of its guitars. This feature will make the guitar one of the best available in the market. An evidence of this is that he buys more spruce wood than any other guitar company. But what if the buys more spruce wood because it sells more guitars in the market than any other competitor and not because its guitars' top will be make full of spruce?

Answer choice analysis
A) While mahogany can be used to make laminated tops for guitars, spruce is used only to make solid tops. Irrelevant
Comparison between different kinds of wood to build the tops of guitars is not in discussion

B) Wender’s competitors buy rosewood, which is also reputed to make guitars with excellent acoustics. OFS
A competitor's decision to chose a different wood for its guitars doesn't show a flaw in the argument.

C) Wender sells more guitars than does any other company. Correct!
This could open the possibility that Wender purchases more spruce to built more guitars and not to built one of the best guitars in the market (with a full spruce top)

D) Wender’s guitars are much more expensive than those of its competitors. Irrelevant
Price of sender's guitars is irrelevant for the argument.

E) While spruce can be used to make good acoustic and electric guitars, experts believe that using East Indian rosewood results in better classical guitars. OFS
This option is incorrect because it narrows the scope to specifically one type of guitars : classical guitars. So the result of the use of East Indian rosewood in better classical guitar is not in discussion.

Hope it helps!

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