Hello, in order:
ustedes
Hay dos pizarrones
leo
You read a blue book
That white lab coat is not ugly
Ana y Luis van a tu clase de arte
Best regards
1: Verónica y yo almorzamos temprano
2: Mi tío pago mi boleto de avión
3: Yo explicó mis planes a mi tío
4: Tú sacas libros de la biblioteca
5: Mi primo juega baloncesto
6: Yo practicó deportes
7: Mis abuelos comienzan a hacer ejercicio
8: Yo llegó tarde del cine
B) they shake each other's hand
The verb in this sentence,"se dan", comes from "darse", which is a reciprocal verb (verbo recíproco) and these verbs always talk about something that the speakers are mutually doing, so the other options wouldn't be correct because: 1) They aren't referring to the 3rd person of plural, 2) They aren't doing a reciprocated action.
Hope this helped you :)
1. Protégete de los rayos del sol.
2. No sumergirse con joyería.
Good luck
Its, what is an earthquake