today. A few years ago, computers (1) .....................very large and expensive. Business managers and rich people ordered them but they (2) ..................... know how to use them. In many countries, however the situation (3) ..................... now completely changed. A lot of people not only own microcomputers but also know how (4) ...................... them. a. Chọn từ đúng cho mỗi chỗ trống 1, a. were b, are c, have been d, is 2, a, don't b, doesn't c, not d, didn't 3, a, has b, have c, had d, are 4, a, used to b, to use c, using d, used ( Làm rồi giải thích nhé )