It's not relevant why preschoolers follow strict routines, just how those routines impact their teachability. Without that information, this isn't helpful.

This weakens the editorialist's argument: preschoolers’ curiosity might not be helpful, because it gives them terrible attention spans, which makes teaching harder.

The editorialist isn’t arguing about older children; we only care about preschoolers. This also doesn't explain how strict systems are helpful. So, it's irrelevant.

Like (C), we’re not interested in comparing preschoolers with older children. This just isn't relevant to how difficult it is to teach preschoolers.

This is irrelevant, because it doesn’t tell us that preschoolers aren’t difficult to teach. Maybe preschool teachers just manage their stress better than other teachers.