Active: Bring a garland of roses.

Passive: [[1]]

 

 

In this sentence the active of a sentence starting with ‘order’.

According to their rule - 

Active: Verb1 + Object

Passive: Let + Subject 1 + be + Verb3

Example:

Active: Bring (Verb1) a garland of roses (Object).

Passive: Let(Subject 1) a garland of roses be(Verb3) brought.

So, the correct answer is "Let a garland of roses be brought".