Construct the requested scale
Check the exercise's written feedback and score after your attempt. Compare letter names as well as pitches; playback alone cannot distinguish enharmonic spellings.
Check the spelling, not just the sound
Separate warm-up: write D major through the octave before opening the worked answer.
Reveal the D-major spelling and reasoning
D E F# G A B C# D follows W W H W W W H. D–E and E–F# are whole steps; F#–G is a half step. G–A, A–B, and B–C# are whole steps; C#–D is the final half step.
If you used F or C natural, check the E–F and B–C gaps: those are half steps where this scale needs whole steps. Gb and Db may sound like F# and C# in equal temperament, but repeat G and D while skipping F and C. Successive letter names require F# and C#.
Close the answer to try this warm-up again, or continue with the exercise's next prompt. This reference adds no score, audio, or saved Progress.