Methyltetrachloride (MTC) is chemical found in some

we dont even need to negate this ..

just going through the argument can give us the answer

+1 A

If it causes less than the 50% of cases, we cannot assure that this policy will reduce the cases in a 50%.

I would also go for A for the same reasons as my friends have listed down....

Easy pick - A
Except option A, none were close to actual assumption.

Premise: Methyltetrachloride (MTC) is chemical found in some pesticides, glues, and sealants.
Premise: Exposure to MTC can cause people to develop asthma.

Conclusion: In order to halve the nation's asthma rate, the government has announced that it will ban all products containing MTC.

MTC………………cause asthma………………ban MTC………………….to halve asthma rate

This conclusion indicates that MTC is ONE OF THE MAJOR CAUSES OF ASTHMA and not any other cause is present. Therefore, it assumes that by banning MTC, asthma rate would go down by half.

Let’s look at the choices:
(A) Exposure to MTC is responsible for no less than half of the nation's asthma cases.
This is the correct choice.
Negated statement: Exposure to MTC is responsible for LESS THAN HALF of the nation’s asthma rate. Then MTC does not contribute much to the asthma rate. There are some other reasons for this. It matches our pre-thinking.

(B) Products containing MTC are not necessary to the prosperity of the American economy.
Prosperity of the American economy is OUT OF SCOPE here because it is not the concern for the government at the moment.

(C) Asthma has reached epidemic proportions.
OK but how does banning MTC helps. INCORRECT.

(D) Exercise and proper nutrition are helpful in maintaining respiratory health.
OUT OF SCOPE. No information on MTC……

(E) Dust mites and pet dander cause asthma.
Irrelevant because it does not tell that is this contribution more than MTC’s or not………

The argument is that the nation's asthma rate will be halved by eliminating MTC products.

This clearly assumes that a direct proportionate drop of 50% in the asthma rate by merely banning MTC products, thus it must be true that at least 50% of the population is exposed.

hi sir
in the question thay have mentioned halve the asthma rate but in the prompt A it was written halve the asthma cases

how can both be similar

please clarify
thanks
vibhakar