Tradução:Eles reduziram o álcool neste vinho.
If you can point to it, you can use "that." If you are holding it, use "this."
"Ah," she said, bending down to pick up the ostrich feather, "this is the clue I've been looking for."
"Ah," she said, pointing to the lipstick smudge on the rim of the glass, "that is the clue I've been looking for."
Generally, abstract ideas take "that." That's a great idea.
Eu tirei todas as minhas dúvidas aqui: http://www.brasilescola.com/ingles/demonstrative-pronouns.htm