题干
——The two old friends were ______ busy _____with each other ______ the time.
——Yes. They haven't met for long.
A：too, to talk, to forget
B：too, talking; to forget
C：so, to talk, that they forgot
D：so, talking, that they forgot
答案(点此获取答案解析）
D
元，若使用这台仪器的日平均费用最少，则一共使用了