Step 1: Recall the formula.
Osmotic pressure is \(\pi = iCRT\), where \(i\) is the number of particles each solute gives in solution (van't Hoff factor).
Step 2: Note that C, R and T are the same.
All solutions are \(0.1\,M\) at the same temperature, so the only thing that changes \(\pi\) is the factor \(i\).
Step 3: Find i for each solute.
\(KCl \rightarrow K^+ + Cl^-\) gives \(i = 2\). \(CaCl_2 \rightarrow Ca^{2+} + 2Cl^-\) gives \(i = 3\). Glucose and Urea do not ionise, so \(i = 1\) for each.
Step 4: Pick the largest i.
\(CaCl_2\) gives the most particles \((i = 3)\), so it has the highest osmotic pressure.
Step 5: Conclusion.
More particles in solution means higher osmotic pressure.
\[ \boxed{0.1\,M\ CaCl_2} \]