18. In lines 12-14, the phrase the trees defensive mechanism has an impact on moth fecundity refers to which of the following phenomena?
Female moths that ingest phenols are more susceptible to wilt virus, which causes them to lay smaller eggs.
Highly concentrated phenols in tree leaves limit caterpillars food supply, thereby reducing the gypsy moth population.
Phenols attack the protein globule that protects moth egg clusters, making them vulnerable to wilt virus and lowering their survival rate.
Phenols in oak leaves drive gypsy moths into forest stands dominated by aspens, where they succumb to viral epidemics.
The consumption of phenols by caterpillars results in undersized female gypsy moths, which tend to produce small egg clusters.
19. It can be inferred from the passage that wilt disease virions depend for their survival on
protein synthesized from the tissues of a host caterpillar
aspen leaves with high concentrations of phenols
tannin-rich oak leaves
nutrients that they synthesize from gypsy moth egg clusters
a rising threshold of caterpillar vulnerability to wilt disease
20. Which of the following, if true, would most clearly demonstrate the operation of the trees defensive mechanism as it is described in the first paragraph of the passage?
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