Question 1 with 1 blankestos árboles fueron plantados por mi abuelo.
question 2 with 1 blanknosotros analizaremos estos temas.
question 3 with 1 blankla oficina de cobranzas organizó todos los pagos.
question 4 with 1 blankel nuevo cd de la banda zoé habría sido comprado por miles de fanáticas.
question 5 with 1 blanklos pacientes deben ser revisados por el doctor lópez.

Explanation:

1.Estos árboles fueron plantados por mi abuelo.

Those trees were planted by my grandpa.

In this sentence, we used passive voice. Which means, the trees is an object in this sentence, and the action is performed by the subject, which is my grandpa. Compared to the active, in passive a subject ( my grandpa ) is in focus because the action is performed upon him.

2.Nosotros analizaremos estos temas.

We analyze these themes.

This sentence is in active. Because we is the subject and the action that is being performed is analyze. Which means, we are performing the action against the verb, not vice-versa.

3.La oficina de cobranzas organizó todos los pagos.

The collection office organized all payments.

This sentence is also in active. The collection office is in the subject in this sentence, it's the agent of the sentence ( subject that is active ). The verb we used is organizar, which belongs to the first group of verbs, ending in ar, it is a regular verb.

4.El nuevo CD de la banda Zoé habría sido comprado por miles de fanáticas.

Zoé's new CD would have been bought by thousands of fans.

This sentence is in passive voice. The '' el nuevo cd de la banda zoe '' is subject and the verb '' habria sido comprado '' is in passive. The subject in this sentence receives all the attention, which means the action is occurring against it, by the '' thousands of fans''

5.Los pacientes deben ser revisados por el doctor López.

Patients should be reviewed by Dr. Lopez.

This sentence is also in passive voice.  In this sentence, '' Dr Lopez '' is an agent and it performs the action against '' the patients ''. The verb we used is deber, which belongs to the third group of verbs ending in ir, and the verb revisar belongs to the first group, ending in ar

6. Estos temas son analizados por nosotros.

These themes are analyzed by us.

This sentence is in passive voice. The agent of the sentence is '' us '' and all the attention goes to the subject '' these themes ''. The verb we have here is analizar, which belongs to the first group of verbs as it ends in ar, and it is a regular verb.

7. Mi abuelo plantó estos árboles.

My grandpa planted these trees.

This sentence is transformed from the passive voice to the active.

The subject is my grandpa, the object is these trees.

The verb we used in this sentence is plantar, which is a first group's verb, as it ends in ar. It is a regular verb in Spanish language and it means to plant.

8. Todos los pagos fueron organizados por la oficina de cobranza.

All payments were organized by the collection office.

The agent in this sentence is '' collection office '' and it's taking an action against the '' all payments '' which is an object. When it comes to passive, all the attention gets the object.

9. Miles de fanáticas comprarían el nuevo CD de la banda Zoe.

Thousands of fans would buy new CD from band Zoe.

The sentence is in active voice. The subject of the sentence is '' thousands of fans '' and the object is '' cd from band Zoe'' The verb we used here is comprar, it belongs to the first group of verbs as it ends in ar, and it's a regular verb.

10. El Dr. López debería revisar a los pacientes.

Dr. Lopez should review patients.

The sentence is in active voice. The subject of the sentence is '' Dr Lopez '' and the object is '' patients ''. The verbs we have here are deber and revisar -- the first one belongs to the second group of verbs and the second one belongs to the first group of verbs because of their endings.