Which of the following is correct?
a. my father has just won a trip to australia.
b. my father has just won a trip to australia.
c. my father has just won a trip to australia.
d. my father has just won a trip to australia.

The sentence that is written correctly is C. My father has just won a trip to Australia.

A.  is wrong because Australia is a proper noun and should be capitalized.

B. is wrong because father in this case is not a proper noun and should not have been capitalized and Australia is a proper noun and should be capitalized.
 D. is wrong because father in this case is not a proper noun and should not have been capitalized.

Hope this helps.:)

a, overstatement is the answer

what’s the sentence so that can you