One of the following is the Toyota DNA Activity Rule.

a$.$

Any improvement must be made in accordance with the scientific method, under the guidance of a teacher, at the lowest possible level in the organization.

b$.$

Every customer$-$supplier connection must be direct, and there must be an unambiguous yes$-$or$-$no way to send requests and receive responses.

c$.$

The partway for every product and service must be simple and direct.

d$.$

All work is highly specified as to content, sequence, timing, and outcome.

e$.$

Every product and service should flow along a simple, specified path