Answer:
- Preposterous.
Step-by-step explanation:
As per the question, the boldfaced word that best accomplishes the given sentence would be 'preposterous' as the another option goes completely out of context. The word 'preposterous' implies 'something absurd or ludicrous which is contrary to common sense' that appropriately fits to the context of the sentence and completes as well as accomplishes its meaning. After using this word, the sentence would imply that however, in earlier times the consideration of Earth as flat was an accepted fact but for today's scientist it is simply 'preposterous' or 'senseless or shocking'.