19 is preterite. 20 is imperfect. 21 is conditional.
Depends on what you want to say, since "Tomar' has two meanings.
"Tomar", as in drinking and "tomar", as in taking.
I honestly don't think there's actually a formal way of saying tomar. It depends on the sentence & how you want to address the person.
Ex. Usted se puede tomar el agua? Can you drink the water?
Ahora, ustedes tomaran el examen > Now, you'll take the exam (but in a polite way!)
If you have any more doubts feel free to ask me!
Question: ¿Qué comerá Anna?
Answer: Anna comerá pizza.
Question: ¿Cuando regresará José?
Answer: José regresará mañana.
