Questions 11-17: Identify the correct possessive form. 11. His sister's-in-law/sister-in-law's letter came as a surprise to Chuck. 12. Arizona's/Arizonas' climate is dry. 13. She is writing a paper on Byron and Shelley's/Byron's and Shelley's poems. 14. I met a man whose/who's sister I know. 15. It's too bad that the dog's/dogs' foot got hurt. 16. Smith's/Smiths' house is red. 17. Kevin and Mike's/Kevin's and Mike's parents, Arthur and Alice Brooks, are both scientists.

First you should know that possessive pronouns replace a name or a noun that indicates possession, to whom something belongs. With this explained, the answer are:

His sister-in-law's letter came as a surprise to Chuck (the apostrophe goes at the end of the last word)

Arizona's climate is dry (the apostrophe goes at the end of the word)

She is a writing a paper on Byron's and Shelly's poems (the apostrophe goes at the end of the second name because the entity is not the same)

I met a man whose sister I know (because it reffers to his sister)

It's too bad that the dog's foot got hurt (the apostrophe goes at the end of the word)

Smith's house is red (the apostrophe goes at the end of the surname)

Kevin and Mike's parents, Arthur and Alice Brooks, are both scientists (the apostrophe goes at the end of the second name because the entity is the same)

11. His sister-in-law's letter came as a surprise to Chuck.

The compund noun is not separated. The 's is added to the end of the noun.

12. Arizona's climate is dry.

The possessive of a singular noun is formed by adding an 's to it.

13. She is writing a paper on Byron's and Shelley's poems.

Since the poems belong to two separate people--they did not compose them together, so this is not shared ownership--the 's goes after each of their names.

14. I met a man whose sister I know.

Who's is a contraction meaning "who + is", expressing "what or which person or people". Whose is a possessive pronoun.

15. It's too bad that the dog's foot got hurt.

This is the same case as number 12.

16. Smith's house is red.

If a singular noun ends in s, the rule is to also add 's. The only time a noun ending in s will only have an apostrophe added is when is plural. So in this case it could only be Smith's or Smiths's, depending on the name, since it's not a plural noun.

17. Kevin and Mike's parents, Arthur and Alice Brooks, are both scientists.

Kevin and Mike share the same parents. As this is a shared possessive, the 's goes at the end of the last name.