39. 燃氣渦輪機循環的輸入熱量為 \( q_{in} \),渦輪機輸出功為 \( W_t \),壓縮機輸入功為 \( W_c \),則其熱效率的定義式為何?(A) \( q_{in}/(W_t + W_c) \)(B) \( q_{in}/(W_t) \)(C) \( (W_t - W_c)/q_{in} \)(D) \( (W_t + W_c)/q_{in} \)