Answer: D. Turing conceived the structure of a programmable computer.
Explanation: The passage describes how Alan M. Turing described the theoretical aspect of a programmable computer. There is no reference to a physical machine or Turing working on an actual (physical) computer.
The Turing machine, although it does sound like a physical computer was an abstract idea, conceived in mathematical form of what a programmable machine would be like. Alan Turing is considered one of the founding fathers of theoretical computer science.