What question does Holden request Stradlater to ask Jane?
Holden is clearly agitated to learn Stradlater is taking Jane Gallagher on a date. Holden met her two summers before and is obviously fond of her. Holden asks Stradlater not to tell Jane that he was kicked out of Pencey Prep. He worries about Stradlater exploiting her because he considers Stradlater "a sexy bastard" who shows interest only in Holden's recollection that Jane's stepfather used to "run around the goddam house, naked. With Jane around, and all."
Holden's relationship with Jane was a chaste one; he tells Stradlater they "used to play checkers all the time." Holden remembers one of Jane's endearing quirks and tells an unimpressed Stradlater,
She wouldn't move any of her kings. What she'd do, when she'd get a king, she wouldn't move it. She'd just leave it in the back row. She'd get them all lined up in the back row. Then she'd never use them. She just liked the way they looked when they were all in the back row.
Holden tells Stradlater, "Ask her if she still keeps all her kings in the back row."