Gloria is the manager of a plant in Iowa that manufactures baby furniture. She wants workers to be more productive so the plant can avoid being closed down and the work being shifted overseas. Which one of the following approaches or techniques should Gloria emphasize?

A) Theory X
B) Unionization threat
C) Hawthorne effect
D) Scientific management

Scientific management emphasizes finding the most efficient way to complete tasks through standardization and specialization, which can lead to increased productivity. This approach would be most suitable for Gloria's goal of increasing productivity and avoiding closure of the plant. Theory X assumes that workers need to be controlled and directed, and unionization threats may lead to conflict rather than increased productivity. The Hawthorne effect refers to the phenomenon where workers improve their productivity simply because they are being observed or given attention, but this effect may not be sustainable in the long term.