Irregular verbs

Most verbs have past tense and past participle in –ed ( worked, played, listened). But many of the most frequent verbs are irregular. Example:

I want to build a sand castle like the one we built last year.

→ In this example, the irregular verb build is in base form. The irregular verb built is the past simple form of “build”. When you look at the complete list of examples, you’ll notice that built is also the past participle of the irregular verb “build”.

Visit the following link and keep on practicing :)
http://www.englishexercises.org/makeagame/viewgame.asp?id=2030