Which of the Following Is the Most Concise Sentence

Which of the following is the most concise sentence?

A) Bad luck.
B) It is apparent and obvious, therefore, that sound knowledge of letter composition and cultivation of the accurate thinking by which it must be accompanied should constitute an exceedingly worthwhile accomplishment.
C) Graduate students looking for good teaching jobs face an uncertain future.
D) In the case of the spaceship, there is an uncertainty factor as to whether the data communicated from it will be satisfactory in respect of the aims of the experiment.