You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Doctor_Who

Context:
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.

Question:
What is the only episode released on VCD?

The Infinite Quest