If the implications of the answer are ambiguous, i.e. if the answer choice can either weaken or strengthen the argument depending on other, unknown factors, then yes - I'd say this is a good reason to eliminate it.
There is no reason to suspect that (A) weakens the argument. The argument is essentially causal: the author observes a decrease in likelihood of serious injury since 1955, which coincides with the introduction of the new legislation. From this, the author concludes that the new legislation was responsible for the increased worker safety:
New Legislation Increased safety
This may be so, but answer choice (A) presents an alternative cause: technological innovation! This is an alternative cause that could easily explain the increased worker safety, weakening the argument.
Answer choice (E), by contrast, has no relation to this causal argument. Maybe workplace safety conditions have improved across all industries - so what? This could be the result of the same legislation that the author believes improved worker safety in the high-risk industries. If anything, since the legislation does not appear to target high-risk industries in particular, answer choice (E) can easily be interpreted as strengthening the conclusion of the argument.
Hope this helps!
I understand why A is the correct answer. However, if we assume E is talking about global industries (Not only within the certain country). Would this answer choice choice weaken the argument?
Changing the answer in the way you suggest does not weaken the claim that the explanation in that country is its legislative changes, especially since that could be the explanation in the other countries as well.