It is so hard.
Right now G is trying to learn when to put an "-s" on the end of words versus "-ed". It is not easy.
I will run.
She will run.
Jerry will run.
They will run.
Most words use "-ed" to show past tense.
I will help.
She will help.
Jerry will help.
They will help.
Is it any wonder that some deaf people write with conflicting verb use? It's taught in 1st grade and they haven't had the benefit of hearing it for 6 years prior to being given rules to guide what they know intuitively because it sounds right.
Os the subject of S or Z sound we're trying to come up with rules that are less esoteric than "use Z sound after voiced consonants." We know:
-se says Z
-es says Z
-ss says S
-ce says S
-s after voiced consonants (B, G, D, M, N, V, W, L, R) says Z
-s after unvoiced consonants (P, C, K, T, F) says S
And I thought verb tense agreement was hard.