2) Ben Higgs has got one child.Sam O'Dell hasn't got one child.He's got two children.
3)Ben Higgs has got three fish.Sam O'Dell hasn't got three fish.He's got two fish.
4)Ben Higgs has got one sheep.Sam O'Dell hasn't one sheep.He's got two sheeps.
5)Ben Higgs has got three mice,Sam O'Dell hasn't three mice.He's got two mice.
mouse (единственное число)------mice(множеств.,)