Williams can play . . . . . . . . piano. A. a B. an C. the D. no article

The correct answer is D. no article.

The word “piano” is a common noun, which means it refers to any piano in general. We do not use articles with common nouns unless they are specific or unique. In this case, there is no reason to believe that Williams is playing a particular piano, so we do not use an article.

Here are some examples of when we would use an article with the word “piano”:

• Williams can play the piano very well. (This indicates that Williams is playing a specific piano, such as the piano in his living room.)
• Williams can play a piano. (This indicates that Williams is able to play any piano, not just a specific one.)
• Williams can play the piano sonata in C major. (This indicates that Williams is playing a specific piece of music for the piano.)

I hope this helps!