In active/passivebwhen to avoid by + subject in the passive form

Question

She ordered the family to be shifted.

1. The family were ordered to be shifted by her.
2. The family were ordered to be shifted.

My query in this question is: Out of the two passive forms which one should be chosen? As per format first should be the correct one because by + subject is the actual format. But the answer to this question is 2nd option. We avoid by + subject only in those cases where subject is generally a universal fact such as by police.

Secondly family is a single entity so we should be using was rather than were.

Suggestions please.

Answer 1

There is no grammatical or semantic rule. The governing factor is pragmatic: you omit the agent of the action if it is unnecessary to the meaning you are trying to communicate. Some examples:

• You omit the agent because your hearers can supply it from their knowledge of the world or the circumstances ... For instance, if you say that somebody was given a parking ticket you don't generally need to add that the ticket was written by a meter maid or traffic cop.

• You omit the agent because it's not important to your discussion ... For instance, if you are primarily concerned to tell people that a friend was hit in a traffic accident, it's probably not important to tell them who was driving the car that hit her.

• You omit the agent because you want to suppress the involvement of the agent ... For instance, a company may admit that "mistakes were made", without openly acknowledging that it was the company or company employees who made the mistakes.

• You omit the agent because you don't know who it is.