The following initial-rate data were collected for the reaction X + Y → products.
Trial [X]₀ (M) [Y]₀ (M) Initial rate (M·s⁻¹)
1 0.100 0.100 2.5×10⁻⁴
2 0.100 0.300 7.5×10⁻⁴
3 0.200 0.100 5.0×10⁻⁴
Identify which pair of trials is most appropriate for determining the reaction order with respect to Y, and briefly explain why that pair is chosen.