Provide the IUPAC names for the following compounds: 1) CH3C(CH3)2CH2OH 2) Cyclohexane with two OH groups.

The structure can be expanded as:

      CH3
      |
CH3 - C - CH2 - OH
      |
      CH3

The longest continuous chain containing the $\text{OH}$ group has 3 carbons. This is a propane derivative.

The $\text{OH}$ group is on the first carbon.
The chain is: $\text{C}1\text{H}_2\text{OH} - \text{C}2(\text{CH}_3)_2 - \text{C}3\text{H}_3$.

There are two methyl ($\text{CH}_3$) groups attached to carbon 2.

The parent alcohol is propan-1-ol. With two methyl groups at position 2, the name is 2,2-dimethylpropan-1-ol.

The IUPAC name is $\boxed{\text{2,2-dimethylpropan-1-ol}}$.

2) Cyclohexane with two $\text{OH}$ groups

The compound is a 6-membered carbon ring, which is a cyclohexane. It has two hydroxyl ($\text{OH}$) groups, making it a diol.

The two $\text{OH}$ groups are on adjacent carbons. Therefore, they are at positions 1 and 2.

The name is cyclohexane-1,2-diol.

The IUPAC name is $\boxed{\text{cyclohexane-1,2-diol}}$.

3) Cyclopentane with four methyl groups

The compound is a 5-membered carbon ring, which is a cyclopentane. It has four methyl ($\text{CH}_3$) groups attached to the ring.

Starting from the top carbon as 1 and moving clockwise, the methyl groups are at positions 1, 2, 3, and 4.
(C1: top, C2: top-right, C3: bottom-right, C4: bottom-left, C5: top-left).

There are four methyl groups, so "tetramethyl". Their positions are 1,2,3,4. The parent ring is cyclopentane.
The name is 1,2,3,4-tetramethylcyclopentane.

The IUPAC name is $\boxed{\text{1,2,3,4-tetramethylcyclopentane}}$.