Answer:
1. I study, he/she studies
I studied, he/she studied
I will study, he/she will study
2. I am studying, he/she is studying
I was studying, he/she was studying
I will be studying, he/she will be studying
3. I have studied, he/she has studied
I had studied, he/she had studied
I will have studied, he/she will have studied
Explanation:
Verbs are words that express actions, occurrences, and states of being. One of their most important categories is tense.
There are three main tenses in English: past, present, and future. For events that took place in the past, we will use the past tense. For events that are taking place at the present time, we will use the present tense. For events that will happen sometime in the future, we will use the future tense. Depending on the nature of the action we're talking about, we will use different types of tenses (simple, progressive/continuous, or perfect tense).
You can see more about these tenses in the images attached below: