Answer: B) Teachers use educational apps such as Operation Math Code Squad to make learning interactive.
Explanation: a topic sentence is a sentence that expresses the main idea of the paragraph in which it occurs. From the given options, the one that would best support the main idea is the corresponding to option B, because the topic sentence claims that tablets and smartphones are being used in classrooms to connect education and technology, and in option B we can see an example of how that is done (teachers using apps to make learning interactive).