Đáp án:

- Nearly a billion mobile phones are sold ... (a)

- The first mobile phone call was made ...

- The call was answered ...

- The first mobiles were powered ... (a)

- Voicemail was added ...

- Internet access was not added ... (b)

- The first text message was sent ...

- It was not typed ... (b)

- The camera phone was invented ...

- Photos of his newborn daughter were shared ... (a)

- In the UK, a mobile phone is stolen ...

- What are mobile phones used for the most? (c)