Context: High-definition image sources include terrestrial broadcast, direct broadcast satellite, digital cable, IPTV (including GoogleTV Roku boxes and AppleTV or built into "Smart Televisions"), Blu-ray video disc (BD), and internet downloads.

Question: Roku and AppleTV are examples of what?
Answer: IPTV

Question: Internet downloads, Blu-ray videos, and Apple TV are examples of what?
Answer: High-definition image sources

Question: Terrestrial broadcast and direct broadcast satellite are examples of what?
Answer: High-definition image sources

Question: Digital cable and Roku are examples of what?
Answer: High-definition image sources

Question:  Roku and AppleTV aren't examples of what?
Answer: Unanswerable

Question: Internet downloads, Blu-ray videos, and Apple TV aren't examples of what?
Answer: Unanswerable

Question: Digital cable and Roku aren't examples of what?
Answer: Unanswerable