题干
— Have you seen my email about our TESL project?
— Yes. Luckily, I checked my emails yesterday. Normally, I _____ my email-box for days.
— Yes. Luckily, I checked my emails yesterday. Normally, I _____ my email-box for days.
A：haven’t opened
B：didn’t ope
C：hadn’t opened
D：don’t ope
答案(点此获取答案解析）
D
的部分在磁场中，当管内充满血液并通以横穿管子的电流时血液便能向前流动。为使血液在管内不流动时能产生向前的压强P，电流强度I应为