You add an -es onto nouns that end in which letter?

The correct response is that you add an -es to nouns that end with s, ch, or x. This rule applies to ensure proper pronunciation and to form the plural of nouns that create difficulty when simply adding -s.

When a noun ends in s, the pluralization requires -es to articulate the plural form distinctly (for example, "bus" becomes "buses"). Similarly, nouns ending in ch (like "church") or x (like "box") also require -es for the same clarity in pronunciation, becoming "churches" and "boxes," respectively.

Thus, the answer encompasses all three scenarios, confirming that the addition of -es is necessary for nouns that end in s, ch, or x.