this is my yellow tshirt变成复数形式的句子 tshirt通常以复数形式出现么?

These are my yellow t-shirts.

these are my yellow t-shirts

These are my yellow T-shirts.

This is are yellow and white dog变成复数形式？~

There are yellow and white dogs.

不是的。有时单数，有时复数
1）"这个"需用单数形式：This is a yellow tshirt.
2)"这些"就需要用复数形式：There are yellow tshirts.

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