We develop our impressions of other countries and their people through books, movies, television, magazines, fellow students, and friends. But is there really any substitute for first-hand experience？
Come, spend a summer studying in the USA, and get to know people and a land which are incredibly rich in their variety. You may end up on an urban campus or a rural one, at a small school or a large one, in a cool climate or a warm one, in San Francisco or St. Louis. But whatever your experience, it will be first-hand, personal, alive, and unforgettable!
If you spend a summer studying in the USA, you'll have advantages which the tourist never will. Not only will you learn the subject matter of your choice, but you’ll gain an understanding of the American educational system as well. You'll experience the culture of the people and the dynamics of your physical environment. But above all, as a student you'll have a chance to meet Americans. Get to know them, communicate, exchange ideas and opinions, and hopefully form. friendships which will endure beyond the length of your stay in the USA.
The following articles will help you in deciding which summer program to choose, what to bring, and how to adjust to the life in the USA. But the first and most important decision is one which you can make right now. Why not say, "This summer, I'll be studying in the USA!"
According to the passage, our impressions of other countries and their people are usually developed ______.

A. through first-hand experience
B. in the very countries
C. through friendships with people
D. through various sources of experience