Answer:
La maestra baila
Ellos cantan
El chico compra
Los estudiantes contestan
Yo converso con mis padres
Tu estudias español
Nosotros llegamos
Usted dibuja.
Yo descanse
Ella trabaja
Explanation:
For most adjectives, the endings are like this:
o : masculine singular
os : masculine plural
a : feminine singular
as : feminine plural
La abuela means the grandmother. It is a feminine singular word. Therefore, you use the ending -a, so the answer is vieja.
Also, keep in mind that the adjective endings match noun endings. Abuela has the ending -a, so the adjective should also end in -a.
