＜そうですね＞

そうですね is used in basically two ways.

First, show your agreement or understanding on someone's remark.

Second, make time to think when we are asked some questions.

You can also use そうだね instead of そうですね in the casual speech.

＜なるほど＞

なるほど is used to show that you understand someone's remark or explanation.

＜ええ＞

ええ is used to show that you are actively listening to what the speaker talks.

ええ is used in the formal speech.

You can say うん in the casual speech.

References:

Basic Japanese Daily Phrases

https://anchor.fm/yuya-sato/episodes/Basic-Japanese-Daily-Phrases-emg8q3

Random Useful Expressions

https://anchor.fm/yuya-sato/episodes/Random-Useful-Expressions-en3j7l

Random Useful Expressions 2

https://anchor.fm/yuya-sato/episodes/Random-Useful-Expressions-2-enbbrk

Random Japanese Slangs

https://anchor.fm/yuya-sato/episodes/Random-Japanese-Slangs-epeboc

Random Japanese Slangs #2

https://anchor.fm/yuya-sato/episodes/Random-Japanese-Slangs-2-eptu4n

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