"Is it woollen?"
Why was this question marked down to -1? It is a perfectly legitimate question.
I typed "είναι μάλλινος" too and got the same reply as the poster above. I had to think for a while before I figured it out.
"it" in English is neuter so μάλλινο is the correct answer but the sentence in English is a bit ambiguous.
There is no way for us to know the gender of the object referred to. The Greek αυτή and αυτός are also translated as "it" in English when not referring to persons.
So in going from English to Greek, context is needed to decide if "it" refers to a masculine or feminine or neuter noun.
I hope this is helpful to the original poster.
There's nothing wrong with "Αυτό είναι μάλλινο." We probably missed. It has been added as a translation, thank you. ^.^
(However, keep in mind that the pronoun is not necessary, The addition of αυτό would make it a bit more specific than it needs to be, with the meaning of this rather than it.)
Many times the word order changes to give emphasis. For example "Αυτό είναι μάλλινο;" simply asks the question - I really don't know if it is woolen or not. "Είναι αυτό μάλλινο;" or "Είναι μάλλινο αυτό;" seem to put more stress on "αυτό" and show incredulity - I doubt that it's woolen.