was, were
[解説] 
■ 「・・だった」「・・でした」を be動詞 で表わすには,was,were を使います・
 
単数
複数
 
現在
過去
現在
過去
1人称
I am
I was
we are
we were
2人称
you are
you were
you are
you were
3人称
he is
she is
it is
he was
she was
it was
they are
they were
※ are は were になります。
   am,is は was になります。

I was busy yesterday. (私は昨日忙しかった。)
They were busy yesterday.(彼らは昨日忙しかった。)

■ 疑問文
Was ..?
Were..?
 になります。

Was he busy yesterday? (彼は昨日忙しかったですか。)
Were you busy yesterday?(あなたは昨日忙しかったですか。)

■ 否定文
was not...(省略形は wasn't...)
were not...(省略形は weren't...)

I wasn't busy yesterday.
You weren't busy yesterday.