单项选择题
Which of the following is true?
A.The sale of smart phones, according to IDC, will make up about two-thirds of all sales by 2017.
B.In 2000, more than 30% of mobile phone subscriptions in the world were in developing countries.
C.Over 75% of smart phone users are still in developed countries.
D.By 2012, there were approximately six billion mobile phone subscriptions in the world.