Katie Owns 100 Pairs of Shoes

Katie owns 100 pairs of shoes.All of Katie's shoes are present in a warehouse.Katie sells her 100 pairs of shoes to Jane.Jane agrees to pick up the shoes from the warehouse.Katie drives to Jane's house and drops off a warehouse receipt for the shoes.Jane then drives from her house to the warehouse to pick up the shoes.When does passage of title occur?

A) when Jane enters into the contract to buy the shoes from Katie
B) when Jane pays Katie for the shoes
C) when Katie drops off the warehouse receipt to Jane
D) when Jane goes to the warehouse and picks up the shoes