On What Basis Did Herschel Think He Had Found a Comet

Multiple Choice

On what basis did Herschel think he had found a comet?

A) The object appeared as a small greenish disk in his telescope.
B) It appeared to be moving slightly night by night.
C) No star appeared in that position on his charts.
D) It was not a point of light, like a star should appear.
E) All of the above are correct.