Final answer:
Option A is correct: David Tennant, Matt Smith, Christopher Eccleston, Tom Baker, and Peter Capaldi are five actors who have portrayed incarnations of the Doctor in the British television series Doctor Who.
Step-by-step explanation:
The five actors who have portrayed incarnations of the Doctor in the British television series Doctor Who are found in option A: David Tennant, Matt Smith, Christopher Eccleston, Tom Baker, and Peter Capaldi. These actors have contributed to the evolving narrative of Doctor Who, each bringing their own unique interpretation to the character of the Doctor, an alien Time Lord from the planet Gallifrey who has the ability to regenerate into a new form.
It's important to note that these are not the only actors who have played the Doctor; the show has a long history and several others have also filled the role. However, each actor listed has had a significant impact on the series during its run. Moreover, David Tennant and Matt Smith are particularly well-known among the newer generation of fans for their portrayals during the show's revival in the 21st century.