Which of the following grammars is considered an s$-$grammar?

$G_1=(V,,R,S)$

$SaS|bAS|aB$

$Ab|aA|cC$

$Ba|b|c$

$Ca|b|$

$G_2=(V,,R,S)$

$SaS|b|cSA$

$Aa|bA|cAA$

$G_3=(V,,R,S)$

$SaS|b|bSS$

$AaA|b|cAAA$

$G_4=(V,,R,S)$

$SaS|bB|cC$

$A$aAA$|aS|b$

$Ba|b|c$

$CaC|bB|$