急求一篇关于学习英语时,学习者需要学会说“谢谢,请,对不起”为什么要学会说三个词.

There is a saying, "when in Rome, do as the Romans do ", which means when you are visiting another country, you should behave like the people in that country. That's why learning to say "sorry", "please" and "thank you" is very important when you are in a western country. Because western people tend to say the words, please, thank you and sorry more often. If you don't do the same, they will think that you are rather rude.
sorry
to show that you feel bad about something that you have done and take responsibility for it
if you touch someone by accident, even just brush their arm or touch their leg in the bus – just say, “sorry”
if you get in someone’s way by accident – “sorry”
if you ask them to repeat something – “sorry, could you repeat that, please?”
please
whenever you want someone to do something for you or give something to you (in a shop, for example). When I go to the shop and the cashier doesn’t say please when telling me how much I have to pay, I must say I get rather offended.
thank you (please note that this is TWO words!)
if someone does something for you or gives something to you, you say thanks (or thank you). If my cashier down at the shops fails to thank me for my payment, I will think they are rude and/or that their parents perhaps could have taught them manners a little more successfully.