A.where can we buy the tickets

B.how much it costs to fly to Shanghai

C.who is he waiting for

D.why was he late for school this morning

【答案】B

【解析】

考查宾语从句引导词、时态及语序。句意：我不知道飞到上海的费用是多少。这里在说一个客观事实，所以句子用一般现在时态，且宾语从句只能用陈述语序，再结合句意，故选B。