The structures for active/passive voices for modal verbs are:

Active: Subject + modal verb + verb (Ist form) + object...

Passive: Object + modal verb + be + verb (IIIrd form) + by + subject...

So, with the help of the above structures, we can convert the given sentence into passive voice: Books can be bought online from Amazon.

Hence, option C is the correct answer.

The active voice of imperative sentences which suggest order, suggestion or request can be made in the following way:

Active: Verb + object

Thus, the sentence in the active voice will be: Please consider my request.

Hence, option D is the correct answer.

The given sentence is in the present perfect tense, and it is in the passive form.

The structures for active/passive voices are :-

Active: Subject + has/have + verb (IIIrd form) + object.

Passive: Object + has/have + been + verb (IIIrd form) + by + subject.

So, the active voice of the given sentence would be: Jyoti has forgotten the keys.

Hence, option B is the correct answer.

The given sentence is in active voice. It is in the present continuous tense.

The structures for active/passive voices are:

Active: Subject + is/are/am + verb (ing) + object…

Passive: Object + is/are/am + being + verb (IIIrd from) + by + subject...

So, with the help of the above structures, we can convert the given sentence into a passive voice: The patient is being treated by the doctor.

Hence, option B is the correct answer.

The given sentence is in the active voice. It is in the simple past tense.

The structures for active/passive voices are:

Active: Subject + verb (IInd form) + object...

Passive: Object + was/were + verb (IIIrd form) + by + subject...

So, with the help of the above structures, we can convert the given sentence into passive voice: Their creative potential was maximized by their emotionally intense collaboration.

Hence, option B is the correct answer. 

Structure of active voice: Subject + verb(IInd form) + object + sub-clause

Structure of passive voice :Object + was/were + verb(IIIrd form) + by + subject + sub-clause

The sentence in the passive voice will be: All the warships of the enemy were easily pulled by Gulliver after him.

Hence, option D is the correct answer.

Therefore, it must be changed to the Passive voice, where something could be done by the subject, and it was ‘passive’.

In order to do that,

1. The object of the transitive verb in the Active voice should become the subject of the verb in the Passive voice (‘the car’ becomes the subject in place of ‘they’).

2. Add the appropriate form of the verb 'be' to the sentence and use the past participle of the verb (‘are lifting’ is converted to 'is being lifted').

3. Add a 'by' followed by the doer of the action.

Thus, the same sentence in the Passive voice is ‘The car is being lifted with a crane'.

Hence, option C is the correct answer.

The given sentence is an interrogative sentence and it is in the present perfect tense. It is in the active form.

The structures for active/passive voices are:-

Active Voice :- Has/Have + subject + verb (IIIrd form) + object?

Passive Voice :- Has/Have + object + been + verb (IIIrd form) + by + subject?

So, with the help of the above structures, we can convert the given sentence into passive voice:- Has this beautiful artwork been created by you?

Hence, option C is the correct answer.

The given sentence is in active voice. It is simple form of present tense.

The structures for active/passive voices are:-

Active: Subject + verb (“s“ or “es” with singular noun) + object.

Passive: Object + Is/are/am + verb (IIIrd form) + by + subject.

So, based on the above structures, we can convert the given sentence into passive voice:- Every day the house is vacuumed and dusted by the maid.

Hence, option A is the correct answer.