Which of the following is/are NOT out of these five 5S?

A Japanese tool called 5S (each step starts with letter “S”) is a systematic program that helps workers take control of their workspace so that it actually works for them (and their customers) instead of being a neutral or, as is quite common, competing factor.

Which of the following is/are NOT out of these five 5S?
A . Seiton
B. Seiso
C. Shitsake
D. Seiku

Answer: C, D