Regarding "NOTE" in 第0課 - Hiragana: Diacritical Marks

[pugpenguin]

I think which sound is used by which characters is mixed up here.

[pugpenguin]

I may be wrong though and maybe this specific exercise(Multiple Choice) just tells the wrong sounds these characters make.

[SethClydesdale]

Hello @pugpenguin,

These four kana are part of what's called the Yotsugana. In modern standard Japanese, ぢ & じ and づ & ず are pronounced virtually the same. The only difference you might see is in their romanizations dzi/di for ぢ and dzu/du for づ.