Voice

The given sentence is in Passive Voice. As per the question we have to change it into Active Voice.
The structure of the given sentence as follows: Subject+has/have+V3+Object.
(Active Voice) Subject (Objective Case)+has/have+been+V3+Object (Subjective Case).
(Passive Voice) 'The plan' will be put in place of 'we'.
(Subject becomes object) And 'We' will be put in place of 'The plan'.
(the object becomes subject) 'Have looked at' will be changed into 'Has looked at'.
(To agree with the changed subject and object) Thus the correct sentence is:
The plan has been carefully looked at

In Active Voice, a sentence emphasizes the subject, performing an action. In Passive Voice, a sentence emphasizes the action or the object of the sentence.
The given sentence is in the active voice and 'We' is the subject and 'Liza' is the object.
When we convert this sentence into passive voice, the subject 'We' of the active voice becomes the object 'us', the object 'Liza' becomes the subject.
The passive format "is + V3 (regarded)" should be used. This is the active and passive voice rule for the present simple tense.

Some nouns are not made plural by adding 's/es'. It is done in a different manner.
Criterion- criteria, mouse- mice, phenomenon- phenomena, radius- radii, syllabus- syllabi, etc.
For example: You don't fulfill the criterions set by the commission.(wrong)
You don't fulfill the criteria set by the commission.(Right)
We need the plural form of the given noun in the sentence i.e. mice.

The given sentence is an example of Active Voice. As per the given question, we have to change it to Passive Voice.
The process of transformation is as follows:
The subject of the given sentence is 'They'.
The object of the given sentence is 'Elaborate'.
The subject will be put in place of the object and the object will be put in place of the subject.
'Are making' will be changed into 'are being made'.
However, the subject 'they' will not be used as 'by them' because it becomes the hidden subject here. This is so because here the action is the central focus and the actor can be any unknown/general entity.
Thus the correct sentence is: Elaborate arrangements are being made for the party.

The given sentence is in a passive voice form, hence we need to convert it into an active voice form.
We need to follow these instructions while changing the voice of an interrogative sentence.
The inverted form of the verb i.e. Did you leave, will commence the sentence.
The given sentence is in the simple past tense.
The active voice form for the simple past interrogative sentence:
Helping verb (Did) + subject + V1 + object? At last line up the remaining part.
Following these steps, we finally get- Did you leave your bag in the bus?