You would need to introduce a list.
For example you could have: My shopping list contains of; milk, bread, and yogurt.
Another purpose is to separate clauses.
Answer: proud, committed is the answer
Answer: the most important to help project your image is to be confident all the time.
Explanation: because if you show people a good attitude and a confident personality they will trust you easily and also, if you dress appropriate and clean all the time, people will take you seriously.
C. I found a bag of marbles.
This is the only sentence that contains an indefinite article. Indefinite articles are "a" and "an" for singular nouns. "some" is the indefinite article used for plural or uncountable nouns.
"the" is a definite article.
