>先生に質問ないですかと聞かれた時いつもnoと言っていますが丁寧な言い方ないかなといつも疑問です。
どの言語もこの辺は似ているかと思いますが、
文章を長くすることによって、より丁寧な雰囲気を作れます。
なので、「質問ないですか？」に対して、
単に「No.」と答えるよりは、
-----------------------
No, not at this time.
No, not this very moment.
No, not at the present moment.
No, not right now.
No, not that I can think of.
-----------------------
などと答えるのはいかがでしょうか。
また、「sir」・「ma'am」など挿入すると、更に丁寧な印象となります。
↓
例：
-----------------------
Teacher:
Any questions, Taro?
Taro:
No, sir, not right now.
-----------------------
After saying 'no', it is advisable to thank the teacher for having asked if you have any questions.
Otherwise if there is something that you do not quite understand and he does not ask you, the lesson will proceed without you understanding what you have just gone through.
You then add, 'I don't have any questions'.
By saying this, you are confirming to the teacher that you definitely don't have any questions, that you understand what you have just gone through.
no'と言った後、質問がないか尋ねてくれた先生には感謝しましょう。
でなければ、自分が次にわからないことがあった時に、先生が尋ねてくれないかもしれませんからね。
理解できていないのにレッスンが進んで行くことになってしまいます。
'I don't have any questions'. といえば、今やっている部分に関して質問はない、と先生に確認する言い方です。
'No' is not an impolite word in itself and saying 'No' to this kind of question is not a rejection or rebuff in any way. With the two phrases above, you could say, 'No' first for clarity. When someone asks a closed question ie a question which would normally be answered 'yes' or 'no,' they expect to hear 'yes' or 'no' before any explanation. In fact, if you do not say yes or no, that may seem impolite!
You can make any sentence sound polite by adding "thank you"in the end.
By saying "all clear", you notify the teacher that you have no questions and the content of the class is clear and understood.
最後に "thank you" を加えると、どんな文も丁寧になります。
"all clear" と言って、授業がしっかり理解できて、質問がないことを伝えています。
If you would like to say no to someone politely when they ask you something, you can say something like "No thank you" or "I'm good, thanks" while waving your arms in a "no" like manner. These are polite ways of turning something down or saying no to something.
When you say everything is fine, that means you are content with what you have learned, or satisfied with the service done for you. Saying "that will be all" means that you are happy with what you have learned or happy with whatever service was given.
"Everything is fine." と言うと、教わったことあるいは相手のサービスに「満足している」という意味になります。
"That will be all" と言うと、教わったことやサービスに「満足した」という意味になります。
アメリカ合衆国 
イギリス 
南アフリカ 
ニュージーランド 
