Take a look at the following two sentences:
1) The midterm exam was graded the teacher.
2) The teacher graded the midterm exam.
The first one uses passive tense (“graded by the teacher”). In English class—and in writing in general—this use of the passive tense is taboo. So you can bet the SAT would always choose the active tense in second sentence over the first passive voice used in the first one.
But passive voice on the SAT is a little subtler than that. Take a look:
1) Considered overly sentimental, Sergei Rachmaninoff was at one time ridiculed by music critics.
2) Music critics at one time ridiculed Sergei Rachmaninoff for being overly sentimental.
3) Music critics were at one time ridiculing Sergei Rachmaninoff for the reason that they thought his music overly sentimental.
A little tougher, right? So let’s start with the first sentence, which is passive tense (notice the “by music critics”). At first glance, you would eliminate it. The thing is the SAT does not technically consider this passive construction incorrect. See, the sentence is complex, using the phrase to describe Sergei Rachmaninoff (“Considered…”). So the passive tense is okay.
You can also write sentence #1 in active tense, as sentence #2 shows. Notice that sentence #2 is even a little shorter, which the SAT typically likes.
Here is the thing: you would most likely never have sentence #1 and #2 as answer choices (though, if for some reason the SAT did split hairs like this, always choose an error free sentence in active voice over an error free sentence in passive).
How the SAT tries to trick students is by creating a sentence in active voice that is actually not grammar free. Notice sentence #3 above. Sure, it’s in active voice; however, it is kind of wordy (“for the reason that” vs. “because”). If you had to choose between #1 and #3 always choose #1, a sentence that is grammar free but that uses the passive voice.
To simplify things:
Active > Passive
Passive > Active (but wordy)
Passive > Active (but with grammatical errors)
One last thing to watch out for is the word “by”. In other words, just because you see “by” does not mean a sentence is using the passive voice.
1) Refrigerators work by cooling ammonia and releasing heat back into the surrounding environment.
2) By studying every day, you can do well on the SAT.
3) The senior members banished him from the club by first taking a vote.
In the three sentences above, “by” is used as “through” or “by means of”. They are not the result of taking a verb, slapping a “by” in front of and putting the resulting verb before a noun.
So remember, if a simple sentence is in the passive voice, “He was considered a genius by his contemporaries”, the SAT is most likely going to have an answer that is a grammar free and in active voice. Pick this one. However, in more complex sentences, sometimes the SAT will favor passive voice. In which case, the other answers will probably have something wrong with them. Don’t just choose them because they are in active tense.