Q: Given a prompt and four completions, select the completion that is the most plausible in continuing or answering the prompt. This task is designed to test common sense and has various categories ranging between idioms, negated statements, polysemy, subject referencing, and quantitative reasoning. Generate either Completion A, Completion B, Completion C, or Completion D.
Prompt: In old times, people thought that the Earth was flat. It is because 
Completion A: the Earth is actually flat. 
Completion B: they were misinformed. 
Completion C: they have not been to the other side of the planet. 
Completion D: although the Earth is spherical, in five dimensional hyperspace the Earth is flat.
A:
Completion B