Carlos Has a Basis in His Partnership Interest of $30,000

Carlos has a basis in his partnership interest of $30,000. He receives a current distribution of $6,000 cash, unrealized receivables (FMV $11,000, basis $10,000) , inventory (FMV $8,000, basis $4,000) , land held as an investment (FMV $7,000, basis, $6,000) , and building (FMV $21,000, basis $9,000) . The partners' relative interests in the Sec. 751 assets do not change as a result of the current distribution. Carlos's basis in the building is

A) $6,000.
B) $9,000.
C) $7,500.
D) $2,500.