In this task, you're given a question, along with a context passage. The passage will not have a direct answer to the question, but can include some information and a clue for the answer. Assuming you can only obtain information about one entity in the passage, your job is to determine whether information from the passage can be used to answer the question. Indicate your choice as 'a' for Yes or 'b' for No.

Question: Who directed the 1993 Doctor Who charity special? Passage:The effect was also used well throughout the whole 1993 Doctor Who charity special Dimensions in Time and in dream sequences of the 1997 3rd Rock from the Sun two-part season 2 finale Nightmare on Dick Street. In many countries in Europe, a series of short 3D films, produced in the Netherlands, were shown on television. Glasses were sold at a chain of petrol stations. These short films were mainly travelogues of Dutch localities. A Power Rangers Lightspeed Rescue movie called Power Rangers in 3D: Triple Force (later broadcast as two-part Trakeena's Revenge) sold on VHS through McDonald's purportedly used "Circlescan 4D" technology, which is based on the Pulfrich effect, but there was very little 3D present. In the United States and Canada, six million 3D Pulfrich glasses were distributed to viewers for an episode of Discovery Channel's Shark Week in 2000. Animated programs that employed the Pulfrich effect in specific segments of its programs include Yo Yogi!, The Bots Master, and Space Strikers; they typically achieved the effect through the use of constantly moving background and foreground layers.
a