Respuestas
1- Nobody had studied with Sally for the test.
2- Mark hadn’t eaten anything when he got home.
3- No one had ever practiced French when they visited Paris.
4- Ross had taken a shower when someone rang the bell.
5- They hadn’t had enough money to buy a house until they won the lottery.
6- The prisoners had nowhere to run after the police let the dogs out.
7- I didn't eat anything until he had finished making the sandwich.
8- We had been here several years before.
9- Some of my friends had traveled to Canada to learned French.
10- None of the politicians had been really honest in the history of any country.
El Past Perfect se usa para señalar acciones que sucedieron antes de otro suceso. I had already taken a shower when we ran out of water.
¿Qué sucedió primero? I had taken a shower = Yo me había bañado
¿Qué pasó después? when we ran out of water = cuando se fue el agua.
Usamos los Pronombres Indefinidos cuando no nos vamos a referir a ninguna cantidad, cosa, persona o lugar en particular, dicho de otra manera, (no estamos especificando).
¿Qué no estamos especificando?
Cantidad
Persona
Cosa
Lugar
Espero te sirva.