This is ___ watch and that is ___ . ?

The sentence "This is ___ watch and that is ___." requires the correct possessive pronouns to appropriately refer to ownership. The options provided include different forms of "you" and "my," necessitating an understanding of how each fits grammatically.

Option A, "yours/mine," is incorrect because while "yours" can refer to ownership of the item in the second part of the sentence, the first blank does not grammatically align as “this” implies possession relating to the speaker, not the listener.

Option B, "my/yours," is the best choice. "My" correctly indicates that the speaker is owning the watch mentioned ("This is my watch"). Meanwhile, "yours" in the second part indicates that the watch referred to is owned by the listener ("that is yours"). This maintains a coherent distinction between the two parties' possessions.

Option C, "your/yours," is also incorrect because "your" cannot be used as a standalone possessive in the first blank when referring to an object. Finally, Option D, "my/you," fails as "you" is not a possessive pronoun.

Thus, option B efficiently conveys ownership, making it the correct and coherent choice for the sentence structure.