The manager was known for his __________ attention to detail.

The sentence "The manager was known for his __________ attention to detail" requires an adjective that describes a meticulous and diligent approach. The correct answer, "assiduous," perfectly fits this context. "Assiduous" means showing great care, attention, and effort; it implies a persistent and diligent application to a task. A manager with assiduous attention to detail would be someone who meticulously reviews every aspect of their work, ensuring accuracy and thoroughness.

Let's examine why the other options are incorrect:

• Careless: This word means not paying enough attention or thought to avoid harm or error. It is the direct opposite of what the sentence implies about a manager known for their attention to detail.
• Lazy: This describes someone unwilling to work or use energy. A lazy manager would certainly not be known for their strong attention to detail.
• Hasty: This means done with excessive speed or urgency; hurried. Hasty actions often lead to errors and a lack of detail, again contradicting the sentence's meaning.

Therefore, "assiduous" is the only word that accurately conveys the manager's reputation for careful and diligent attention to every minute aspect, making it the most appropriate choice to complete the sentence.