The correct option is
A Janet was given a present by her colleagues when she retired.
The given sentence is in the active voice, as the subject 'Janet's colleagues' performs an action 'gave' against the object 'a present'.
If this sentence is changed to passive voice, then the object takes the place of the subject and vice versa and the word
'by' is introduced as now the subject receives the action by the object.
The verb form of the sentence is also changed from active form to
passive.
'Subject (Janet's colleagues) + verb (gave) + indirect object (her) + direct object (a present)' changes to:
'New subject (Janet) + verb (was given) + direct object (a present) + by + new object (her colleagues) + adverbial (when she retired)'
This can be seen in option A, hence it's the right answer.
Option B: Because of the word 'to', the meaning of the sentence is vague and different from the original.
Option C: The word 'by' is missing here.
Option D: 'Is being given' expresses continuous tense whereas the given sentence is in simple past tense.
Hence options B, C and D are incorrect.