Test
        Yourself: Using Both Indefinite and Definite Articles
        Now that you have reviewed the use of indefinite
        and definite articles before nouns, you can test your knowledge
        with this quiz. In the following paragraphs, decide which article
        should be used before a noun, depending on a) whether the noun
        that it precedes is countable or non-countable and b) whether
        the noun has been identified to the reader. Select one of the
        following to "fill in the blank": a, an,
        some the, or no article. Click on the blank
        space to see the correct choice and an explanation.
        
          Paragraph
          1
          ___ reaction was acidified, causing ___
          release of carbon dioxide. Next, ___
          carbon dioxide was evacuated from ___
          flask.
          Paragraph
          2
          Jenny poured ___
          gels to use for electrophoresis. ___
          gels were composed of two different concentrations: 8% and 12%.
          ___ 8% gels were placed
          in ___ cold room overnight.
          Paragraph
          3
          ___ investigators have not yet enrolled enough patients
          in ___ clinical trial.
          ___ tardy investigators
          will be notified by ___
          fax.
        If you would like to see the entire paragraph
        with all of the articles, click on each paragraph heading above
        (for example, "Paragraph 1").