I studied tea ceremony from elementary school to high school. I studied that the Earth is round. I studied the difference between the past perfect and the past perfect continuous tenses. I studied the most I ever have in my life. I studied the most I have ever studied in my life now. I studied the structure of Ainu families. I studied this past-question collection and reviewed it many times. I studied till about 10 o'clock. I studied using this book. I studied very devotedly during summer vacation this year. I studied very hard, only to fail the examination. i studied vs i have studied