The possessive pronoun is <em>"your"</em>.
You left <u>your</u> bike out in the rain today.
A possessive pronoun is that part of any sentence that provides "ownership" to something or to someone. It substitutes a noun sentence.
Examples:
The shirt is <em>mine</em>.
That is <em>her</em> pen.
Take <em>your</em> ball.
What words are possessive pronouns? Mine, yours, his, hers, its, ours, theirs.