The widespread availability of refrigerators ( ) greatly to food safety in many countries since the second half of the 20th century.
1. contributes
2. has contributed
3. will have contributed
4. had contributed
四択97【問題】
The widespread availability of refrigerators ( ) greatly to food safety in many countries since the second half of the 20th century.
1. contributes
2. has contributed
3. will have contributed
4. had contributed