1, The most serious source of danger is essentially the same in 1973 as it was in 1972.
2. One of the obstacles that prevent driving from becoming far easier is the unexpected, hazardous road conditions.
3. So successful was Grace L. Hill at conveying her underlying message through topical plots and contemporary characters that by 1940 her book had sold some three million copies.
이 문장들좀 해석부탁드릴게요ㅜㅜㅜ