For or SinceFor is used for general periods of time - 3 hours, four days, six months.
Since is used for a specific time - 2001, January, last week, one month ago.
Exercise # 1
Click the answer button to see the correct answer.
Exercise # 2
Make sentences using "for" or "since".
Example: How long have you been studying English?
I have been studying English since 1999.