U.S. Environmental Advocate: The government must consider legislation

The first bold sentence is what the Advocate wants to say - the point he wants to put across. Hence it can be called his position or conclusion. It is certainly not a premise which is a statement that supports the conclusion.
Hence, (B), (D) and (E) are the only possibilities.

The second bold statement is an analogy presented showing how a similar action in another country led to the desired effect. So it supports the conclusion.
It does not present a causal relationship. Note that just because it happened in Canada, it cannot be called a causal relationship. A causal relationship would be something like "A causes B". What is given to you is "in case of Canada, A caused B". This is a specific example supporting our conclusion or we can call it an analogy (comparing similarities - this is what happened in Canada so it could happen here too).
Hence, out of (B), (D) and (E), only (E) works.

Answer (E)