What four letters of the alphabet would scare off a burglar?

The post office has thousands of letters.A theif is afraid four letters.What are they? The post pffice has thousands of letters.A thief is afraid four letters.What are they? The post oficehas thousands of letters.A thief is afraid of four letters.What are they?The post oficehas thousands of letters.A thief(小偷） is afraid of（害怕） four letters.What are they? The post office has thousands of letters.A thief is afraid of four letters.What are they? The post office has thousands of letters.A thief is afraid of four letters.What are they What is ‘apple plus four letters? What four letters of the alphabet would scare off a burglar? Which four letters are thieves afraid of? The post office has thousands of letters.A thief(小偷) is afraid of four letters.What are they?不是翻译这道题，是用英语回答这道题 the post office has thousands of letters.A thief is afraid of four letters.What are they?十万火急!帮帮我回答 What four letters could end a game of hide and seek?请尽快!四个字母~最好是大写的 A thief is afraid of the four lettersOICU.Dou you know why?What letter is a question? 1.a thief is afraid of the four letters''oicu''.do youk know why?2.what letter is aquestion? what two words contain thousands of letters What has thousands of letters in it? What has thousands of letters in it? what to words contain thousands of letters What is Honorary Doctor of Letters degree?