It's describing the chica, which is singular and also feminine, so therefore we must use la.
Answer:
it is used for outgoing or recurrent actions in the past
The answer is son because you have to conjugate.
1- supieron
2 - tendrá
3- protegerá
4 - para, por
5- actuarán
Hope it helps ❤️
Infinitivo: Dormir, hacer
Que yo: Arregle
Que tu: Duermas
Que nosotros Arreglemos, hagamos
Que ellas: Hagan
