If the length of each side of a rectangle increases by $10\textbackslash\%$, by what percentage does the area of the rectangle increase? 
选项为:A:$$42\textbackslash\%$$  B:$$21\textbackslash\%$$  C:$$10\textbackslash\%$$  D:$$10.5\textbackslash\%$$  E:$$11\textbackslash\%$$  请回答其中一个选项.