6) She was my teacher at .... Oxford University.
Explanation: The article 'the' is generally not used with the titles of major universities and major public buildings.
7) Maria went to ..... Itlay to attend a marriage.
Explanation: Articles are not used before the names of countries.
8) Peter went to .... United States to spend holidays.
Explanation: The countries whose name contains common nouns like state, republic, or union usually have the article 'the' before their name.
9) ....Asia is the largest continent in the world.
Explanation: Articles are not used with the names of the continents.
10) He works in .... old office building.
Explanation: We speak about a particular building, so we use the definite article 'the'. The word 'Old' starts with a vowel, so the article 'an' can be used if we are not talking about a particular building.