What's the passage written about?

Read the following passage and choose the item (a, b, c, or d) that best answers each of the questions about it.

 Nowadays, you don’t need to be at home or at the office to use the phone. You can carry a mobile phone in your pocket or keep one in your car. With a mobile phone, anyone who can talk and walk can also phone and walk. You don’t have to look for a pay phone to make a call anymore.

Now you can take your calls with you everywhere.

pay phone = public telephone 

What is the passage written about?

• A. the office
• B. public telephone
• C. mobile phone
• D. making a call