B.

Author prefers machine X ONLY because of the quality of goods produced by it & mentions it only produces 2% defective goods.

if machine Y also, only produces 2% defective goods... is the basis of arguing against the author's position of prefering machine X over Y.

This is a comparison question. We first need to follow the argument. Machine Y produces more units per hour than machine X. Thus, the company is going to stop using X. The author says, not so fast, Machine X should still be used because it produces superior quality products than Y and uses the defective rate as support.

A) is wrong because we don't know how old Machine Y is, nor do we know how age factros into the quality the parts.

B) is correct because it shows that based on the defective rate - the support the author uses to indicate X is superior Y - Y and X are equivalent. If Y and X are equivalent in quality, then it makes sense to go with the Machine that produces more units per hour.

C) is wrong because we're talking about X and Y. A new machine is irrelevent to the author's argument or whether we should keep X.

D) This is a separate argument completely. Yeah, Machine Y might make more units than X and it might be less expensive and might have 100 other advantages. The author however focuses on QUALITY. That's the reason Machine X should be used. It is better quality than Machine Y. Therefore, the correct answer choice must relate to the quality of the units.

E) is wrong because it desn't counter the author's position. The author says that Machine X SHOULD be used. Detailing what a position or policy is does nothing to counter the author's normative argument.

The management at a certain company opposes the use of machine X, since machine X produces 5 percent fewer units per hour than does machine Y. However, management is neglecting to consider that the quality of the units produced by machine X is superior to the quality of those produced by machine Y. For example, only 2 percent of the units produced by machine X were found to be defective. Therefore, the managers’ objections are invalid; the company should use machine X.

The argument is in support of machine X. It claims that although machine X produces less units per hour, it produces better quality units than machine Y, given that only 2 percent of machine X units are defective.

Which of the following, if true, could best be used as a basis for arguing against the author’s position that the managers should use machine X?

The correct answer choice demonstrates why machine X should not be used.

A) Machine X is 5 years old. We can't make a comparison without Machine Y's age.

B) Two percent of the units produced by machine Y are defective.

This would mean that machine X and Y produce the same quality of units and machine X still falls behind in efficiency and should not be used

C) The managers have been analyzing a new machine that produces 10 percent more units per hour than does machine X.
We're concerned with machine X's superiority. Also, since we're considering defective units, we have no information on the quality of the new machine.[i]

D) Machine X is more expensive to maintain than is machine Y.
[i]We're concerned with the performance of the machine, not the cost to maintain it.

E) The quality of the product is often not the sole consideration when deciding which machine to use.
It's already stated in the stimulus that efficiency is also a consideration.

"i do not agree with the answer and the reasoning because we are told that x produces 5 percent fewer units per hour than does machine Y so lets take some numerical values, suppose y produces 100 units so x will produce 95 units so 2% of 95 is still less than 2% 0f 100 so how can the defective rate be equal for both machines. Still machine X is more efficient, on the other hand choice D says that X costs more in maintenance which is precisely the concern of the management i.e cost saving so D should be the answer."

I see why one would think that. But I believe the question is saying that 2 percent and 5 percent of the same number of units (as opposed to the 2 percent and 5 percent of the units that X and Y produce in the same hour). Cost is not relevant to the argument. The stimulus provides no information on the concern of management with cost savings.

my take :
option B
consider Machine X is producing 95 units per hour
machine Y is producing 100 units per hour
machine X is short in production by 5 units in comparison to machine Y (that's what the argument states)
now if 2 % of the 95 units are defective , remains 93 units (not-defective)
as for machine Y per option B (we will have 98 units not defective) thus a bigger number than machine Y and same quality.WEAKENS