imhimanshu
Thanks igotthis for the reply.
However, can you please clarify this: Argument says that:
a regulation in force since 1960 has prohibited sale of fruit on which any TDX residue can be detected.Isn't it mentioned that amount of TDX residue should be Zero?
the change will not allow more TDX on fruit than was allowed in the 1960's becauseThis is how I interpreted the Argument:
1) You can't apply TDX because of regulation. If your fruits tested positive, you will not be allowed to sell.
2) Now you can apply TDX in limited amounts.
But
The amount of TDX cannot be more than that was allowed.
As per my analysis, if you are not allowed to apply TDX in 1960s.. then how can question stem says so..?
Where I'm going wrong. Please correct.
Dear Himanshu,
I got your p.m. and I'm happy to respond.

I believe you are being a bit naive about the scientific measuring process. The physical world and its details do not stop existing at the limits of science's ability to measure. There are all kinds of things in the world that we know exist, or that we suspect probably exist, but they are beyond the current ability of science & technology to measure. There are other things, at the atomic and subatomic level, that cannot be measured, not because of the limits of technology, but because of the fundamental limits of matter and energy at that level --- that gets into Quantum Mechanics, which is well beyond the level of science you need to know for the GMAT. You do need to realize, though, that "what can be measured" and "what really is" are not necessarily identical.
In this argument, the sentence, "
a regulation in force since 1960 has prohibited sale of fruit on which any TDX residue can be detected" implies "
can be detected, according to whatever technology they had in the 1960's." Now, maybe in the 1960's, they could detect TDX down to the very last molecule, so they would know exactly how much was there and could detect even the smallest portion. Or, maybe their means of measurement were more limited --- they could detect TDX in quantities down to some small number (say, a milligram, or a microgram), and beyond that level, they simply couldn't detect the TDX. We can only guess --- the prompt passage gives us no way to decide how much they could measure in the 1960s.
The OA, choice
(A), suggest that the latter interpretation was correct. In other words, they had very limited abilities to measure TDX in the 1960's --- say, they could measure down to 1 microgram, but not less than that. Then, in the 1970s, say, they could measure much more precisely, down to the 0.001 microgram (i.e. the nanogram), and the trace allowed is, say, up to 1 microgram. Well, in the 1960s, if there was just less than a microgram, then they couldn't measure or detect that amount, and the fruit with that amount would be passable, while if there were just less than a microgram in the 1970s, then the scientist could detect it, but it would now be an allowable level of trace material, and the fruit still would be passable.
My friend, I strongly recommend that you start reading
Scientific American. I think you need to beef up your understanding of how the experimental sciences operate. Reading a couple articles a week from
Scientific American will be a good workout for the science passages you encounter on the GMAT RC, and they will give you the general background you need to make sense of science arguments on the GMAT CR.
Does all this make sense?
Mike