[单选题]If Delta 12G is given a hand-off to Cleveland center while climbing through 7,500ft to an assigned altitude of 12,000ft, the correct phraseology for the pilot’s initial call-up to centre is _______ . A.Cleveland Centre, Delta 12G, climbing to 12,000 B.Cleveland Centre, Delta 12G at 7,500, climbing to maintain 12,000 C.Cleveland Centre, Delta 12G, out of 75 for 12,000 D.Delta 12G, 7500, climbing to 12,000