49.下圖為簡化的TLD（thermoluminescent dosimeter）原理，圖中的甲、乙、丙、丁分別為： (A)甲：conduction band，乙：valence band，丙：electron trap，丁：Compton photon (B)甲：valence band，乙：conduction band，丙：electron trap，丁：TL photon (C)甲：electron band，乙：valence band，丙：conduction band，丁：scatter photon (D)甲：valence band，乙：electron band，丙：electron trap，丁：TL photon