Which of the following are in the correct order from least to greatest?

Convert the radian measures to degrees: 3π/10 = 54°, π/2 = 90°, and 2π/3 = 120°. Comparing these with 60° and 255° gives 54° < 60° < 90° < 120° < 255°. Therefore, the correct order is choice D: 3π/10, 60°, π/2, 2π/3, 255°.

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