Verb tenses matter in GMAT sentence correction for two reasons: meaning and grammar.
Meaning-wise, it matters whether an action is occurring in the past, present, or future. Grammatically, parallelism sometimes requires that certain verbs be in certain tenses.
In parallel phrases, it’s pretty easy to match up which verb tense should be which. However, it can be harder to know from a meaning perspective. So, I’ve put the verb tenses that you need to know for Sentence Correction below, excerpted from my book on GMAT Sentence Correction:
In English, our most common verb tenses are the simple past, present, and future. “I threw the ball”; “I throw the ball”; “I will throw the ball”. If you don’t know which verb tense to choose in a problem, choose one of these.
Some other verb tenses that come up occasionally are
a) progressive verb tenses. These suggest an ongoing action.
In the past, we say “I have run the marathon before”. This suggests I ran it sometime in the past, possibly multiple times. In the present, we say, “I am running,” to suggest that it’s ongoing right now, or “I have been running”, to suggest that it started in the past or is still ongoing. In the future, we say, “I will be running tomorrow morning.”
b) past perfect. This suggests an action that happened before another event in the past.
So, we say, “I had run to the store before I made the cake”. I made the cake in the past, but, before that, I ran to the store.
c) conditional and subjunctive. These suggest things that might happen, if other things happen. Your English teacher would tell you these are verb “moods”, but we don’t need to pay attention to that right now.
So, we say, in the past, “If I ran to the store, I would have made a cake.” Or, in the present, “If I were a rich man, I would buy myself a house”.
d) future perfect. This is the future of the past. So, we’d say, “If I studied hard in elementary school, I would have become a doctor.”
If you want practice on GMAT Sentence Correction questions with detailed explanations, you should purchase my GMAT Sentence Correction book.