Explanation:

Given:
Molecular formula of the alcohol = C6H12OX
Immediate turbidity with cold, concentrated HCI even in the absence of ZnCI2
X can also be obtained by treatment of an ether with excess of CH3MgBr followed by acid hydrolysis

To determine the correct statement regarding X, let's analyze the given information.

1. Molecular formula of the alcohol = C6H12OX:
From the molecular formula, we can deduce that the alcohol contains 6 carbon atoms, 12 hydrogen atoms, and one unknown atom represented by X.

2. Immediate turbidity with cold, concentrated HCI even in the absence of ZnCI2:
This information suggests that the alcohol is a tertiary alcohol, as tertiary alcohols readily undergo dehydration to form alkenes in the presence of concentrated HCI. This leads to the formation of a cloudy or turbid solution.

3. X can also be obtained by treatment of an ether with excess of CH3MgBr followed by acid hydrolysis:
This reaction sequence is known as the Grignard reaction, where an ether reacts with an alkyl or aryl magnesium halide to form a Grignard reagent. The Grignard reagent can then be hydrolyzed to produce an alcohol. Since X can be obtained through this reaction, it suggests that X is an alcohol.

Based on the above information, we can conclude that X is a tertiary alcohol that can be obtained through the Grignard reaction. Now, let's analyze the given options to determine the correct statement.

a) It is 3-methyl-3-pentanol:
This option suggests that X is a tertiary alcohol with a methyl group attached to both the third carbon and the third hydrogen of the alcohol. However, this contradicts the molecular formula of the alcohol, which only contains one unknown atom represented by X. Therefore, option A is incorrect.

b) It is 2-methyl-3-pentanol:
This option suggests that X is a tertiary alcohol with a methyl group attached to the second carbon and a hydrogen attached to the third carbon. This is consistent with the molecular formula of the alcohol (C6H12OX), where X represents a hydrogen atom. Therefore, option B is a possible correct statement.

c) It is 2-methyl-2-pentanol:
This option suggests that X is a tertiary alcohol with a methyl group attached to both the second carbon and the second hydrogen of the alcohol. This is consistent with the molecular formula of the alcohol (C6H12OX), where X represents a hydrogen atom. Therefore, option C is a possible correct statement.

d) Either (b) or (c):
Since both options B and C are consistent with the molecular formula of the alcohol, it is possible that either one could be the correct statement. Therefore, option D is a possible correct statement.

Based on the above analysis, the correct statement regarding X is option C: It is 2-methyl-2-pentanol. However, option D is also a possible correct statement.