Answer:
True
Step-by-step explanation:
We can look at a definition of unity with regards to art, which is "how different elements of an artwork or design work come together and create a sense of wholeness. It can be achieved through proximity, simplicity, repetition and continuation."
Another definition is "created when there is a relationship between the different elements in a design or artwork."
Using these definitions we can decide that the statement is true.
(that being said, there are a few ways to create unity so they don't all have to be the same size)
I hope this is correct and helps, have a nice day!