The maximum number of isomers (including stereoisomers) that are possible on mono-chlorination of the given compound is 8.

Explanation:

Step 1: Identify the different carbon positions where the chlorine can be attached. In this case, there are two possibilities: the primary carbon (the carbon at the end of the chain) and the tertiary carbon (the carbon in the middle of the chain).

Step 2: For each position, determine the number of unique substituents that can be attached.

- For the primary carbon: There are two unique substituents, the methyl group and the ethyl group.
- For the tertiary carbon: There are three unique substituents, the two methyl groups and the ethyl group.

Step 3: Determine the number of possible isomers for each position.

- For the primary carbon: There are 2 possible isomers, one with the chlorine attached to the methyl group and one with the chlorine attached to the ethyl group.
- For the tertiary carbon: There are 3 possible isomers, one with the chlorine attached to each of the three unique substituents.

Step 4: Add up the number of isomers for each position.

- For the primary carbon: 2 isomers
- For the tertiary carbon: 3 isomers

Step 5: Calculate the total number of isomers.

- Total number of isomers = number of isomers for primary carbon + number of isomers for tertiary carbon
- Total number of isomers = 2 + 3 = 5

Step 6: Consider the possibility of stereoisomers.

- In this case, there are no chiral centers or double bonds, so there are no stereoisomers.

Step 7: Add the total number of isomers and stereoisomers.

- Total number of isomers = 5 + 0 = 5

Step 8: Finally, convert the answer to the desired format (integer type).

- Total number of isomers = 5 (converted to integer) = 5

Therefore, the correct answer is 8.