Recently political pressure groups have become far more effective at

Argument:

As a result of the efforts of animal groups, many pharmaceutical and cosmetics companies have reduced their use of laboratory animals, substituting in their place alternative methods of product testing.

Conclusion: Recently political pressure groups have become far more effective at persuading industrial corporations to change.

We need to weaken this claim. That the change may not have been driven by political pressure groups. That the political pressure groups may not have become more effective at persuading change.

(A) Many companies in the pharmaceutical industry have increased their public relations spending in order to counter the activity of animal rights groups.

PR spending of industry is irrelevant. They reduced their use of lab animals as a result of animal groups. If they are trying to counter the damage done by animal groups by spending more on PR, it doesn't weaken the claim that political pressure groups have become more effective.

(B) Before the new methods of testing products are used, they have to be calibrated by comparison tests involving experiments on laboratory animals.

It doesn't matter that the new tests have to be calibrated by using animals in the beginning. The new methods are being used now instead of animals. The animal groups have been successful in putting pressure on the pharma industry.

(C) When companies stop using laboratory animals, they generally go to some expense to publicize this change of policy.

Again, irrelevant. If the pharma companies stop using lab animals due to pressure from animal rights groups, our conclusion is fine. Even if they publicise later that they are not using lab animals to earn some brownie points in the public, it doesn't matter.

(D) The pharmaceutical manufacturers who still use laboratory animals are mostly the smaller firms that have been less subject to pressure group activity.

This strengthens our argument. The larger manufacturers have seen pressure from animal right groups and have given in to other methods. The smaller ones have not been pressurised so are not using other methods. It does seem to imply that animal right groups have been responsible for the change.

(E) The methods of product testing that do not involve laboratory animals are faster and cheaper that the methods that do.

Now this is a twist. If the other methods are faster and cheaper, it is possible that companies are switching not because animal right groups have become more effective at persuading, but because the companies want to save money. This introduces an alternative reason for the switch and weakens the argument's claim.

Answer (E)