Nosotros __________ al lado de un lago.

vivimos
vivemos
vivir
viven

¡_______ la mesa!
Pongo

Ponga

Pone

Pon

¡_______ las ventanas!
Limpia

Limpian

Limpias

Limpiar

Which would be true for forming an informal command?
You use the infinitive of the verb.

You just need to change the tone of your voice.

You use the formal (Ud.) form of the verb.

You use the informal (tú) form of the verb.

2 answers

1. Vivimos
2. Ponga
3. Limpiar
4. You use the informal (tú) form of the verb.
(I'm confident that the first three are correct, but I'm not sure about the fourth one)
Agree with all except 3. It looks like a command, which does not take the infinitive.