Answer:
We must choose the correct pronoun for each option.
They (all girls): in this case, you should use the pronoun "Ellas", because the ones in the group are only girls and are nor in the conversation and the one talking is not in the group.
They (mixed) in this case the pronoun used is "Ellos (works for only men and for mixed groups)
Ricardo y Felipe: Both names are for men and is a plural case, so the pronoun is "ellos"
Tu y yo: There are two persons in the group, and the speaker "yo" is in the group, so the correct one is "nosotros"
Gloria y Miguel: Gloria is a name for woman, and Miguel is a name for a man, so this is a mixed case, the correct one is "ellos"
Isabel y Juana: Both names for women, so in this case, the correct one is "ellas"
Eduardo: This is a name for a man and is singular, so the correct one is "El"
Marta: This is a name for a woman and is singular, so the correct one is "ella"
You all: Here the group is present in the conversation (are listening) so the correct option is "ustedes"
That: this has not gender, the pronoun used here depends on the distance "eso" is used for things that are at a middle distance, "esto" is for things that are close and "aquello" is for things that are far away.
