Add a suitable prefix to form the opposite of the word : 

Balance

The correct answer is option 4 i.e. imbalance.

Key Points

• Balance refers to a state of equilibrium or equal distribution of weight, amount, etc.
• A prefix is a word, letter, or number placed before another. In this case, placing a prefix before the word balanced would give us its opposite.

Important Points 

• The prefix 'im-' would be suitable in order to convert the word into its opposite.
• Therefore, the opposite word is 'im-balance.' It refers to the state of being out of equilibrium.
• Example: An imbalance in certain chemicals leads to disturbances in the brain's function.
   

​Therefore, option 4 has the suitable prefix to which gives the opposite of the word balance.