Here's why:
* Active voice means the subject of the sentence performs the action.
* Passive voice means the subject is acted upon.
Let's break down the sentences:
1. "The test will be offered several times this week" is passive because the test is being acted upon ("offered"). The actor (whoever is offering the test) isn't explicitly stated.
2. "Formal clothing must worn wedding?" This sentence has grammatical errors and isn't clear. However, even if corrected ("Formal clothing must be worn at the wedding"), it would still be passive because the clothing is acted upon ("worn").
3. "You were told to wait until five for delivery" is active because "you" (the subject) is performing the action of being told.
To make the other sentences active, you could rewrite them like this:
* "Someone will offer the test several times this week."
* "They will wear formal clothing at the wedding."