Answer
Tertiary
Work Step by Step
1) Identify the carbon atom directly attached to "OH" group
2) Then count the number of alkyl groups attached to this carbon atom.
1 substituent - primary
2 substituents - secondary
3 substituents - tertiary
In this example it has 3 other "R" groups : 2 methyl and 1 n-butyl group. Therefore, it will be tertiary ( 3 other substituents)