How do you make a word plural that ends in o and is proceded by a vowel?

Most nouns ending in o preceded by a vowel are pluralized by simply adding s; for example:

• cameo, cameos
• kangaroo, kangaroos
• studio, studiOS
• tattoo, tattoos
• video, videos
• zoo, zoos

There are also some nouns ending in o preceded by a consonant that also simply add s; for example:

• auto, autos
• kilo, kilos
• memo, memos
• photo, photos
• piano, pianos
• soprano, sopraos