This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

Let me give you an example: Passage: The French and Indian War (1754–1763) was the North American theater of the worldwide Seven Years' War. The war was fought between the colonies of British America and New France, with both sides supported by military units from their parent countries of Great Britain and France, as well as Native American allies. At the start of the war, the French North American colonies had a population of roughly 60,000 European settlers, compared with 2 million in the British North American colonies. The outnumbered French particularly depended on the Indians. Long in conflict, the metropole nations declared war on each other in 1756, escalating the war from a regional affair into an intercontinental conflict.
The answer to this example can be: When was the French and Indian War?
Here is why: This question is based on the following sentence in the passage- The French and Indian War (1754–1763) was the North American theater of the worldwide Seven Years' War. It is a common convention to write (start year-end year) beside a historical event to understand when the event happened. You can ask questions like this one about dates, years, other numerals, persons, locations, noun phrases, verb phrases, adjectives, clauses etc. which exist in the paragraph.

OK. solve this:
A wide selection of serials are available from BBC Video on DVD, on sale in the United Kingdom, Australia, Canada and the United States. Every fully extant serial has been released on VHS, and BBC Worldwide continues to regularly release serials on DVD. The 2005 series is also available in its entirety on UMD for the PlayStation Portable. Eight original series serials have been released on Laserdisc and many have also been released on Betamax tape and Video 2000. One episode of Doctor Who (The Infinite Quest) was released on VCD. Only the series from 2009 onwards are available on Blu-ray, except for the 1970 story Spearhead from Space, released in July 2013. Many early releases have been re-released as special editions, with more bonus features.
Answer:
What countries are the Doctor Who DVDs available to purchase?