SIMPLE PRESENT

The world is round.
I study every day.

SIMPLE PAST

I studied last night.

SIMPLE FUTURE

I will study tomorrow.

PRESENT PROGRESSIVE

I am studying right now.

PAST PROGRESSIVE

I was studying when they came.

FUTURE PROGRESSIVE

I will be studying when you come.

PRESENT PERFECT

I have already studied Chapter One.

PAST PERFECT

I had already studied Chapter One before I began to study Chapter Two.

FUTURE PERFECT

I will already have studied Chapter Four before I study Chapter Five.

PRESENT PERFECT PROGRESSIVE

I have been studying for two hours.

PAST PERFECT PROGRESSIVE

I had been studying for two hours before my friends came.

FUTURE PERFECT PROGRESSIVE

I will have been studying for two hours by the time you arrive.