1. Analyze each statement about glucose

Option A: Glucose remains in multiple isomeric form in its aqueous solution

In aqueous solution, glucose exists in equilibrium between:

• open-chain form
• $\alpha$-D-glucopyranose
• $\beta$-D-glucopyranose
• small amounts of furanose forms

So glucose does exist in multiple isomeric forms in water due to mutarotation.

Hence, A is correct.

Option B: Glucose is soluble in water because of having aldehyde functional group

Glucose is highly soluble in water mainly because it contains multiple hydroxyl groups $(-OH)$, which form hydrogen bonds with water.

The aldehyde group contributes much less compared to the many hydroxyl groups.

So saying glucose is soluble in water because of having aldehyde functional group is incorrect.

Hence, B is incorrect.

Option C: Glucose is an aldohexose

Glucose has:

• 6 carbon atoms $\Rightarrow$ hexose
• an aldehyde group in open-chain form $\Rightarrow$ aldose

Therefore, glucose is an aldohexose.

Hence, C is correct.

Option D: Glucose is one of the monomer unit in sucrose

Sucrose is composed of:

• one unit of glucose
• one unit of fructose

So glucose is indeed one monomeric unit of sucrose.

Hence, D is correct.

2. Conclusion

The incorrect statement is:

$\boxed{\text{B}}$