IF YOUR INSTRUCTOR HAS ASKED YOU TO WORK ON DIPLOMA TESTS, GO TO THIS SITE:
https://www.thetestingcenter.com/tests/kanem/ and enter your name and password as given to you
by your instructor
You can help yourself to solve a multitude of grammar and writing problems:
Start at my QUIA page for some exercises and games: http://www.quia.com/pages/kanesclass.html
Here are some others that will answer your questions:
Purdue University's great writing and grammar site
These quizzes are fun and the web site gives great explanations of the answers.
Great descriptions of grammar elements
Subject verb agreement
Grammar Monster explains many grammar concepts in an easy to understand way.
This page will help you understand subjects and verbs.
Vocabulary and Grammar Practice Quizzes
Here's how you reach the Bedford Exercises
Here are links to Parts of Speech, Reading and Vocabulary building exercises
ADDITIONAL SITES OF INTEREST
If you want help with English as a second language, start here:
The Visual Thesaurus