The singular form is una libreta
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.
The plural would be the third one c los autobuses
I believe the answer for this question is A or C
Claudia y Nicole ayudan a María a mudarse.
You would use the ellos/ellas conjugation of ayudar because there are two people completing the verb.
