10. Lena is a very good girl. She always (to help) her mother about the house. Today she (to help) her mother since morning. They already (to wash) the floor and (to dust) the furni-ture. Now they (to cook) dinner together.

10. Lena is a very good girl. She always helps her mother about the house. Today she has been helping her mother since morning. They already have washed the floor and have dusted the furniture. Now they are cooking dinner together.

Объяснение:

1. 'She always helps' — это регулярное действие, поэтому Present Simple.
2. 'Today she has been helping her mother since morning' — действие началось утром и продолжается до сих пор, поэтому Present Perfect Continuous.
3. 'They already have washed the floor and have dusted the furniture' — действие завершено, важен результат (пол вымыт, мебель отпылесошена), поэтому Present Perfect Simple.
4. 'Now they are cooking dinner together' — действие происходит прямо сейчас, поэтому Present Continuous.