Answer:
Let the solid be weighed in air.
Explanation:
Active voice is when the speech of a person is spoken or written as it is using quotation marks. On the other hand, passive voice emphasizes the recipient of the verb. The one main difference between the two is in the position of the subject and object in the sentence.
The given statement<em> "Weight the solid in air" </em>is in the active voice. So, to make it into a passive voice, the object will come before the verb and the subject will move to the end of the sentence. But in this case, since there is no particular subject, we can ignore that. And the form of the verb will be changed accordingly.
Thus, the final sentence in the passive voice will be-
<em><u>Let the solid be weighed in air.</u></em>
