Answer:
What technology devices do you use everyday?
Explanation:
Christian is trying to see which technology device is the most popular. The first question doesn't ask about different types of technology devices, but rather the amount of time spent on them. The second asks what they are used for and the third asks if you have a technology device. Neither of these questions answers which device is the most popular, except for the fourth or last option. Which technology devices are used everyday can help him see which one is the most popular.