1. For
2. Since
3. By
4. At
He has been working Since morning.
Since
- Usage: Indicates the starting point of an action or event that continues up to the present.
- Form: Since + specific point in time (e.g., morning, Monday, 2010).
Examples: She has been living here since 2010.
For
- Usage: Indicates the duration of an action or event.
- Form: For + period of time (e.g., two hours, three days, a long time).
Examples: She has been living here for 10 years.