Shouldn't it be suomeksi?
Olen varma, että lause on suomeksi: "Olen varma, että tämä lause on suomea."
Thanks, that makes sense to use the partitive, but never used in this form before. :)
Is the "in" really neccessary?
In another question I was marked wrong for translating "varma" as "certain" instead of "sure" so which is it, does varma mean certain or sure?
I think both should be accepted. Must be another error so if you spot it report :)