Select the option that expresses the following sentence

Solution

In passive voice, the object "the new vaccine" becomes the subject. The verb "have not tested" is changed to "has not been tested" to reflect the present perfect tense in passive voice.
Option 1 correctly reflects the sentence in passive voice using the present perfect tense.
Option 2 uses the past tense, which is incorrect.
Option 3 has an incorrect verb form ("has not tested"), which does not work in passive voice.
Option 4 uses the present continuous tense, which doesn't fit the original sentence's tense.