Backcrawl
= backstroke
🗣️ 情景例句
How many people are there in your family?
您家有几口人？
Ok, bye-bye.
好吧，再见。
But here we come up against the most difficult of all obstacles to contact with people on other planets ----the astronomical distances which separate us.
然而，在和外星人联系中我们遇到的最大困难是分隔我们的天文距离。