choose the plural noon that's spelled correctly. Pianoes, Fathers-in-law, Editor in chiefs.

The correctly spelled NOUN is Fathers-in-law.

Hmmmm. Polyandry?

The plural form of the word "noon" is not one that is commonly used, as "noon" typically refers to a specific time of day rather than multiple instances. However, the correct plural form of "noon" is "noons."

To determine the correct spelling, we can follow some general rules for forming plurals:

1. For nouns ending in a consonant + "o," we usually add "es" to form the plural. For example: potatoes, tomatoes.

2. For nouns ending in a vowel + "o," we typically add "s" to form the plural. For example: zoos, radios.

Given these rules, "noon" ends with a vowel + "o," so the plural form would be "noons."

To address the other options you mentioned:
- "Pianoes" is incorrect. The correct plural form of "piano" is "pianos," following the vowel + "o" rule mentioned above.
- "Fathers-in-law" is correct. This is the plural form of "father-in-law," a compound noun where the plural marker "-s" is added to the main noun ("father").
- "Editor in chiefs" is incorrect. The correct plural form of "editor in chief" is "editors in chief," as both "editor" and "chief" are pluralized with "-s".

Remember that English spelling and grammar can have exceptions, so it's always a good idea to consult a reliable dictionary or style guide if you're unsure about a specific plural form.