Question

A thunderstorm often turns milk sour. Change it into passive voice.

Answer 1

Object = Milk
Subject = A thunderstorm
Verb = turns


Given sentence is present indefinite.

Its passive voice form is

Obj + is/are + verb3 form + by + subject


Hence your answer is

Milk is often turned sour by a thunderstorm.


Hope it helps dear friend ☺️✌️

Answer 2

Milk is often turned sour by a thunderstorm.