Urban planners in Metroville recently proposed planting deep-rooted oak trees along city avenues to expand the tree canopy and mitigate the urban heat island effect. Critics argued that the extensive root networks would crack adjacent underground water pipes, incurring massive municipal repair costs. In response, city planners pointed out that the target avenues are lined with modern flexible polymer pipes rather than traditional brittle clay pipes, concluding that the tree-planting initiative will not lead to pipe repair costs. Which of the following, if true, most strengthens the city planners' argument?
- Flexible polymer pipes have been shown in municipal engineering tests to bend under pressure from expanding tree roots without fracturing or leaking.Cevap
- BExpanding root systems of oak trees exude chemical compounds that gradually degrade polymer material, causing flexible pipes to rupture faster than clay pipes.
- CTraditional brittle clay pipes in older municipal districts currently account for over seventy percent of Metroville's annual water utility maintenance budget.
- DExpanding the urban tree canopy reduces ambient surface temperatures, thereby lowering municipal expenditures on seasonal air conditioning.
- ECities that replaced brittle clay pipes with flexible polymer pipes experienced a significant drop in initial line installation costs.
Cevap
The statement that flexible polymer pipes bend under root pressure without fracturing or leaking most strengthens the argument.
The city planners defend their plan against critics by noting that the target avenues use flexible polymer pipes rather than brittle clay pipes. For this defense to hold, flexible polymer pipes must actually withstand root pressure better than clay pipes. Confirming that polymer pipes bend under root pressure without fracturing directly reinforces the planners' conclusion that pipe repair costs will be avoided.
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Strengthening Causal Defenses by Validating Assumptions