options 2, 3 and 4 change the voice, I think.
No, the voice remains passive, but the mood changes. Here are two sentences that illustrate the active versus the passive voice:
1. I read newspapers.
2. Newspapers are read (by me).
Both are present tense and indicative mood. The modal verbs (aka auxiliary verbs) in English a rather complicated little things, e.g., can implies ability (but nowadays it's often used in a permissive sense, like may). Historically, these verbs were from a different class of verbs in Germanic called preterite-present. They main trait is they exist only in present and past forms, and they do not distinguish between third person singular present and the other persons and numbers, i.e., I may, *I shall may, I can, he can, I read, he reads. Most of our traditional grammar terms come from the Graeco-Latin grammatical tradition. A big difference between Latin and English is that we have very little verbal inflectional morphology left and most of our verbal conjugations are done periphrastically.
