It is "va" because the a in va represents he, she, and you (formal). He is going to the pool, so it is 'Mi padre va a la piscina con nosotros.'
The above answer is wrong. The correct answer is invierno.
The verb
hacer
can be used in various ways to talk about the passage of time. You can use hacer to describe how long ago something happened or how long you have been doing something. You can also use hacer to describe past actions that were interrupted by another action. Hace and Actions that Started in the Past and Continue into the Present
There are two formulas you can use with hacer to talk about actions that started in the past and continue into the present. These expressions are useful for talking about something you have been doing for a certain amount of time. Formula One
hace + time + que + verb in the present
Formula Two
verb in the present + desde + hace + time Examples with Formula One
EXAMPLES
Hace un año que estudian español.
They have been studying Spanish for one year.
Hace seis años que conozco a mi esposo.
I have known my husband for six years.
Examples with Formula Two
EXAMPLES
Habla español desde hace tres años.
He has spoken Spanish for three years.
Tengo mi trabajo desde hace seis meses.
I have had my job for six months.
Hace and Actions that Were Interrupted in the Past
There are three formulas you can use with hacer to talk about actions in the past that were interrupted. These expressions are useful for talking about something you had been doing when something else happened.
In expressions of this type, the interrupting action is conjugated in the preterite.
