Question: How many episodes where in the season of "Doctor Who" broadcast on 29 April 2017 on BBC?

Context articles: 2017 IIHF World Championship Division I
Doctor Who (series 7)
Martin Day
Dreamland (Doctor Who)
Time Lord
Doctor Who (series 10)
Come Sing with Me
Thin Ice (Doctor Who)
Totally Doctor Who
BBC Studios

The 2017 IIHF World Championship Division I was an international ice hockey tournament run by the International Ice Hockey Federation.
 Group A was contested in Kiev, Ukraine from 22 to 28 April 2017 and Group B in Belfast, United Kingdom from 23 to 29 April 2017.
 South Korea and Austria were promoted to the 2018 World Championship.
 It marked the first time South Korea had earned promotion to the top tier of the World Championship.
The seventh series of the British science fiction television programme "Doctor Who" aired from 1 September 2012 to 18 May 2013, being split into two parts, as with the previous series.
 The series was broadcast concurrently on BBC One in the United Kingdom, BBC America in the United States, and on Space in Canada, and also on ABC in Australia, with the first five episodes each released a week after its UK and North American premiere and the remainder released the day after each episode's UK premiere.
 Following its premiere on 1 September 2012, the series aired weekly until 29 September 2012.
 Six episodes were broadcast in 2012, including the 2012 Christmas special, "The Snowmen", which aired separately from the main series.
 The remaining eight episodes began broadcasting on 30 March 2013.
 "The Snowmen" introduced a new TARDIS interior, title sequence, theme tune, and outfit for the Doctor.
Martin Day (born 1968) is a screenwriter and novelist best known for his work on various spin-offs related to the BBC Television series "Doctor Who", and many episodes of the soaps "Fair City", "Doctors" and "Family Affairs".
 He is currently an Associate Lecturer in Creative Writing at Bath Spa University and the Wessex regional representative of the Writers' Guild of Great Britain.
Dreamland is the third animated "Doctor Who" serial (based on the British science fiction television live action series) to air on television, and the second to air after the revival of the live-action series in 2005.
 It stars David Tennant as the Tenth Doctor and aired in six parts (one 12-minute episode, followed by five 6-minute episodes) broadcast daily from 21 November 2009 on the BBC's Red Button service, the official "Doctor Who" website and the BBC iPlayer.
 It was broadcast in its entirety on BBC Two and BBC HD on 5 December 2009.
The Time Lords are a fictional, ancient extraterrestrial species in the British science fiction television series "Doctor Who", of which the series' protagonist, the Doctor, is a member.
 Time Lords are so named for their command of time travel technology and their non-linear perception of time.
 Originally they were described as a powerful and wise race from the planet Gallifrey, from which the Doctor was a renegade; details beyond this were very limited for the first decade of the series.
 They later became integral to many episodes and stories as their role in the fictional universe developed.
 For the first eight years after the series resumed in 2005, the Time Lords were said to have been destroyed at some point between the original series' cancellation in 1989 and the show's revival during the fictional Last Great Time War.
 In 2013, the 50th anniversary special "The Day of the Doctor" concerned this supposed destruction and their eventual survival.
The tenth series of the British science fiction television programme "Doctor Who" premiered on 15 April 2017 and concluded on 1 July 2017, and consisted of twelve episodes, after it was announced in July 2015 that BBC Worldwide had invested in a tenth series of the programme in its annual review.
 The series is led by head writer and executive producer Steven Moffat, alongside executive producer Brian Minchin.
 It is the third and final series overseen by the two as executive producers, as well as Moffat's sixth and final series as head writer.
 This series is the tenth to air following the programme's revival in 2005, and is the thirty-sixth season overall.
Come Sing With Me () is a Chinese variety music show, and it is broadcast on Hunan Television.
 The host by Wang Han and singer Han Hong associate jointly hosted, which invites specialized renown singers and ordinary people like fans to chorus, every episodes approximately taken about 90 minutes to broadcast.
 The program first season have 11 episodes was released on 7 May 2016, and second season have 12 episodes was released on 29 April 2017.
 Mandopop folk singer Fei Yu-ching was associate jointly hosted the final episode of first season, while Han Hong had leave for attending the task on crafts.
 Come Sing With Me also notable as top 10 popular China TV shows of ranked No. 2 in the first half of year 2016.
"Thin Ice" is the third episode of the tenth series of the British science fiction television series "Doctor Who".
 It is written by Sarah Dollard and was broadcast on 29 April 2017 on BBC One.
 "Thin Ice" received mostly positive reviews from critics, with many labelling the topic of racism in the episode as well-executed.
Totally Doctor Who is a children's television series produced by the BBC that was originally broadcast between 13 April 2006 and 29 June 2007, accompanying the second and third revived series of "Doctor Who".
 No episodes have been produced following the third series.
 At the time of its original broadcast, "Doctor Who", a science fiction programme aimed at a family audience, had no existing children's spin-off; "The Sarah Jane Adventures", of which the pilot episode was broadcast on New Year's Day, 2007, would replace the series as the only children's show based on "Doctor Who" until 2009 when "K-9" aired.
BBC Studios is the BBC's commercial production arm.
 It produces many of the highest-rated shows on British television, including "Strictly Come Dancing", "Doctor Who", "EastEnders", "Planet Earth II" and "Top Gear".
 BBC Studios was certified in February 2015 and was separated from BBC Television in April 2016.
 It launched as an independent operating company in April 2017.