这些英语句子怎么改形式?this is a piano（改复数）that knife is short（改复数）is it a spoon?（改复数）are they old cooks?（改单数）are those girls new?（肯定句）are these pencil-boxes old?（肯定句）
问题描述：
这些英语句子怎么改形式?
this is a piano（改复数）
that knife is short（改复数）
is it a spoon?（改复数）
are they old cooks?（改单数）
are those girls new?（肯定句）
are these pencil-boxes old?（肯定句）
答
there are some pianos
those knives are short
are they spoons?
is she/he old cook?
is that girl new？
these pencil-boxes are old
答
this is a piano（改复数）These are pianosthat knife is short（改复数）Those knives are shortis it a spoon?（改复数）Are they spoons?are they old cooks?（改单数）Is he / she an old cook?楼上朋友错了这...