My answer on our previous thread stands, except that (by simply using common sense and having already eliminated answers [a] and [b]) we can now eliminate one more answer:
The whole point about 'synthetic' materials is that, while they might try to emulate natural ones, they're not the same chemically. So that's answer (d) hit on the head.
You're now only left with one possible answer!
[The trick with all such questions is NOT to look for the 'right' answer but to seek out all of the 'wrong' ones and to then see what's left].