Graeco-Latin Square is a form of blocking by one variable. a form of blocking by four variables. a form of blocking by three variables. a form of blocking by two variables.

A form of blocking by three variables.

Step-by-step explanation:

Graeco-Latin square design is a special type of comparative design.

Graeco-Latin square design uses 3 blocking variables unlike the 2 blocking variable as used by the standard Latin square design.

In this square design of experiment, the experimental units are grouped into three different ways.