Answer:

Step-by-step explanation:
We want to conjugate they (feminine) respond.
In Spanish, the feminine they is
. So, we can eliminate the second choice, because it is ellos.
The verb for respond is
. We want to conjugate for ellas.
1. Drop the ending.
- The ending is -er, so drop it.
⇒

2. Add the correct verb ending.
- For ellos/ellas/ustedes and -er verbs, the ending is
.
⇒

Therefore, the correct answer is Ellas responden.