Passage Summary: We have two options for a hedge. One of them won't grow here, so if we want a hedge, we have to use the other one.

Conclusion: If a hedge is used as a screen, it must be made of hemlock.

Reasoning: A hedge screen must be either hemlock or Leyland cypress, but Leyland cypress cannot grow in this specific northern climate.

Analysis: The structure is a classic disjunctive syllogism: if X, then (A or B); Not B; therefore, if X, then A. The argument sets up a limited set of possibilities and then eliminates one based on a factual constraint. To find the parallel, look for a choice that establishes a conditional requirement with two options, proves one option is impossible, and concludes the other must be the choice.