While you will not be asked to identify sentence structures on tomrrow’s test, you do need to understand sentence structure in order to actually understand comma rules. If you don’t understand sentence structure, you’re really just guessing when it comes to comma placement. (By the way, those two sentences were both COMPLEX!)
So, if you need some more practice with identifying simple, compound, and complex sentences (and many of you do!), here are some resources you can use.
For a review of what simple, compound, and complex sentences ARE, you can see the grammar notes under the Grammar for Everyone! tab on this site. If you would like a different explanation, here is a pretty clear explanation of the sentence structures (including compound-complex sentences, which we have NOT covered yet) and their punctuation.
Before tackling sentence structures, you many need to practice identifying phrases (no subject and verb) vs. clauses (subject and verb). You also probably need to review dependent vs. independent clauses. This quiz isn’t very interactive, but it does both. This one also does both and gives some explanation. This quiz just reviews dependent vs. independent clauses.
Once you’re clear on phrases and clauses, you can get a better handle on sentence structure. These quizzes test you on that. Be warned, though, that they both include compound-complex sentences–you don’t need to know those. Yet.