X. Complete the expressions. Follow the model: since yesterday = for 24 hours; for 200 years = since the 19-th century. 1. since 1980 
 2. since Wednesday
 3. since 6 o’clock p. m. 
 4. since December 
 5. since spring 10. 
 6. for 20 years
 7. for 5 days
 8. for the last 2 hours
 9. for 6 months
 10. for a very long time