Ⅰ. hands up 是一句祈使语气的口语，相当于Put up your arms over your head! “举起手来!”如：
① “Hands up, or I’ll shoot.” The policeman demanded the robber. “举起手来，不然我开枪了。”警察命令抢劫犯。
Ⅱ. put up one’s hand 意思与hands up 相同。但语气要弱得多。如：
① Who knows the answer? Hands up / Put up your hands, please. 谁知道这个答案?请举手。
② Put up your hands if you have any question.如有问题请举手。