One oder ones?

Wähle „one“ oder „ones“ für die markierten Satzteile aus.
Just look at those T-Shirts!

1 Oh look! They have some yellow T-Shirts, too.
2 I'll try a red T shirt and a yellow T-Shirt. /
3 You can try a blue T-Shirt.
4 Oh, the yellow T-Shirt is great but it's too expensive.
5 Have they got a cheaper T-Shirt?