Final answer:
The video format most likely used for streaming is h.264, due to its efficiency and compatibility, whereas QuickTime is a multimedia framework and Flash support has declined.
Step-by-step explanation:
In the context of current video streaming technologies, the video format most likely used for streaming is h.264. This is because h.264, also known as AVC (Advanced Video Coding), is widely adopted for its efficient compression and high compatibility with various devices and browsers. In contrast, QuickTime is a multimedia framework developed by Apple that includes a player and other features, but it is not a video codec. Flash used to be a popular format for interactive multimedia content, including video, but has significantly declined in usage and is no longer supported since major browsers and platforms have phased it out, emphasizing instead on HTML5 and other modern streaming technologies such as h.264.