The maximum distance from the origin of a point on the curve \[x=a\text{ }sin\text{ }t-b\]\[\sin \left( \frac{at}{b} \right),\] \[y=a\,\cos \,\,t-b\cos \left( \frac{at}{b} \right),\] both a, b>0, is

• A. a - b                
• B. a+b
• C. \[\sqrt{{{a}^{2}}+{{b}^{2}}}\]        
• D. \[\sqrt{{{a}^{2}}-{{b}^{2}}}\]