What is the pronoun case of the bolded word?

i washed my clothes, but i couldn’t wash yours.

nominative
objective
possessive

It has been two days since you had the opportunity to have lunch with mr. halstead, a wellknown business leader in your community. it was an informal lunch attended by you and six other students interested in learning about his manufacturing business. you thought about sending mr. halstead an electronic card via email him for his time. at the last minute, you decided a handwritten note might be a better option. in your opinion, which type of correspondence would be more effective at getting your message across? explain your answer.