Learn three more sounds: K (kuh), J (juh), and short U (uh), including noticing that K sounds like the earlier C sound.
K says kuh, from the back of your mouth, just like C. J says juh, softer and further forward. U says uh, a short little sound, like in umbrella.
Kuh, juh, uh -- three more sounds ready to learn.
Mastery looks like: They can produce the K, J, and short U sounds and notice that K sounds the same as the earlier C sound.
Common stumbles: Confusing J with the softer "y" sound; stretching the short U into the longer letter name "you."