A student attached two balloons to equal lengths of string and tied them to the same point. The student observed that the balloons repelled each other, as shown in the diagram below. In terms of electrical charges, explain why the balloons repelled each other?

• A. because both the balloons are positively charged
• B. because both the balloon are negatively charged
• C. because one is positively and another is negatively charged                   
• D. either (a) or (b)