_ means that the conditioned stimulus (CS) must not only precede the unconditioned stimulus (US) closely in time, but it must also serve as a reliable indicator that the unconditioned stimulus (US) is on its way. Group of answer choices

The distribution of related animals and plants across the world

Natural selection changes allele frequencies because some survive and reproduce more successfully than others.

What is the best conclusion based on this data? the hypothesis was not supported because the data indicated that fertilizing plants does not improve plant growth. the hypothesis was supported; to get the best growth, use 5 milliliters of fertilizer per plant. the hypothesis was not supported; the data indicated that too much fertilizer can inhibit plant growth. the hypothesis was supported; to get the best growth, use 15 milliliters of fertilizer per plant.