Which characters belong together in 区分开来？ Which characters belong together here?

我们一定要把写字和书法区分开来。
We must differentiate between writing and calligraphy.
We must draw a distinction between writing and calligraphy.
We must separate (区分开来） writing from calligraphy.  

区分：differentiate, distinguish between, draw a distinction
分开：separate
区分开来：separate from??

In () may belong together. I think 3. is maybe the correct analysis.

1a. 我们一定要把（写字区）和（书法区）分开来。

1b. 我们一定要把写字和书法区（分开来）。


我们一定要把写字和书法（区分）开来。
我们一定要把写字和书法（区分开来）。
区分 is the verb, to differentiate.

开 is a resultant complementary, apart.

来 is another resultant complementary, henceforth.

开来 commonly appear together in phrases similar to this one, but they do not form a word. (There is a word 开来 as in 继往开来 which is different).

The affinity of characters is (((区分)开)来) where only 区分 is a word.