What Is the Main Assumption Behind the Scientific-Management Approach or Theory

What is the main assumption behind the scientific-management approach or Theory X?​

A) Employees like variety in their job, responsibility, and a sense of accomplishment.
B) ​The employer should find the best way to do a job and train workers to do it that way.
C) ​Job satisfaction is highly correlated with excellence of job performance.
D) ​The best way to improve job performance is to increase salaries.