plurals?

[allotment10]

what is the plural of this,
is it these or there? sorry, never been any good at english! can someone help, thanks.

[hobbitess]

these

[earthakitten]

These xx

[crofter]

"This book" (singular) becomes "These books" (plural)

On the second point, I think that you may be confusing There (place) and Their (possession);

I would like you to put this book there (or these books there)

That is where they parked their bus.
("their" is always plural and here linked to the word "they")

I hope that this is clearer.

[allotment10]

thanks both of you :-)