Seva
abbr. stand-up extravehicular activity （宇航员在外层空间的）直立舱外活动
🗣️ 情景例句
You are twenty-one, a grown-up young lady old enough to make up your own mind.
你已经21岁了，已经到了可以自己做主的年龄了。
Do you often work out?
你经常锻炼身体吗？
and by measuring the time interval between the taps and the receipt of the echoes, the depth of the sea at that point can be calculated.
测出回声间隔的时间，便可算出该处海洋的深度。