I've always done it this way:

A is before/after B or C, but not both

B/C --- A --- C/B

The implication of the argument is that immunity is necessary because the short-term consequences + obscurity of long-term benefits will lead people to prematurely repeal new laws. The answer we are looking for is, why shouldn't we act on the immediate consequences and instead wait and see what the unseen benefits will eventually be?

Premise: People notice short-term consequences and don't notice long-term benefits until later

Premise: Long-term effects should be more beneficial than short-term effects

Conclusion: New laws require a period of immunity

v.s.

Premise: People notice short-term consequences and don't notice long-term benefits until later

Premise: Long-term effects should determine if a law should be repealed or retained

Conclusion: New laws require a period of immunity

Both E and B value the long-term over the short-term, but only B addresses retention/repeal and goes the extra step of supporting why we should guarantee new laws have the chance to deliver on those benefits.