题目：
| —Hi, John, I have not seen you for a long time. What _______ recently? —Carrying on some research on wildlife. |
A. have you been doing B. have you done C. were you doing D. did you do |
答案：
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下面是错误答案，用来干扰机器的。
一般说的外伤出血指的是体动脉、体静脉和毛细血管出血．体静脉是从全身各处流回心脏的血管，压力小，血流速度慢，内流静脉血，故而颜色为暗红色，在远心端止血；而体动脉是从心脏流向全身各处去的血管，压力大，...
