Final answer:
The plural rule for words ending in 'a' is to either add 's' or 'es' to the end of the word, depending on the specific word.
Step-by-step explanation:
The plural rule for words ending in 'a' varies. In some cases, you simply add 's' to the end of the word. For example, 'apple' becomes 'apples.' However, in other cases, you add 'es' to the end of the word. This is typically done if the word ends in a consonant or a 'y.' An example is 'mango,' which becomes 'mangoes.'