What is "microarchitecture" versus "instruction set architecture" (ISA)?

A The ISA defines the abstract interface (instructions, registers) a processor presents to software; the microarchitecture is the specific internal implementation (pipelines, caches, execution units) used to realize that ISA B Microarchitecture and ISA are exactly the same concept with different names C The ISA describes only the physical transistors on a chip D Microarchitecture refers only to software applications, not hardware