They put their hands behind their backs, so you can't see their hands.
他们将手放在背后，这样你就看不见他们的手了。
初二英语课文
Unit 8 Where do you sit
📚 句中词汇解析
从本句中提取的重要词汇
prep. （表示位置）在…的后面;支持;（表示顺序）在身后;（表示比较）落后于;
adv. 在后面;向后;在后面较远处;（落）在后面;
n. 〈口〉屁股;
💡 be构成一些介词+hind藏在后面→在…后面
"The crowd had to stand behind barriers."
人群只好站在障碍物后面。
近义：back, posterior, rear, rearward, lagging, late
反义：quick, rapid, accelerated