on the possessive pronoun "its"

[achilles]

Good evening, Sir. (Sorry, it's 11:00 pm in Korea)
Today I want to ask you about the possessive pronoun "its".
I saw "The book is mine." "Isn't it yours?" , but I've never seen "the food is its", or "Isn't it its?"
Can't we use "its" in a sentence like "mine, yours, his, hers, theirs"?
In Korea, almost all teachers say there's no possessive pronoun form of "it" and "its" is just a possessive adjective.
Could you please give me an answer to my inquiry? And if possible, I want to see an exemplary sentence using "its" as a possessive pronoun.
Thanks for your kindness.

[hector51]

about the possesive pronounce "its",I have encountered it many times on the news,newspaper...
Newspaper usually use "its" when it want to avoid repeating a name (it can be the name of a country,a firm,a company)if you want to verify,just check out www.cnn.com , you will see how often do they use "its".
For an example:
"Vietnam is doing everything neccesary to join WTO,its efforts are appreciated by the US,but it has to go further....."
Hope it helps!
Cheers

[rewboss]

The dog wagged its tail.

The house stood firm until the sudden earthquake brought its destruction.

The tornado tore through the neighbourhood, bringing destruction in its wake.

The car looks really magnificent, but its engine just isn't good enough.

And here's one from my wife, who doesn't think much of the city of Hanau: The whole of Hanau comes to a stop if a snowflake lands on its edge.

[Naughty Beef]

So what's a possessive adjective?