How many ways A boy can reach the top of stairs which contain 10 steps, when he can take either one or two steps every time?	Choose the correct option:
A) 88  B) 89  C) 90  D) 91  E) 92
case 1:1 1 1 1 1 1 1 1 1 1 &gt; 1!   case 2:1 1 1 1 1 1 1 1 2 &gt; 9!/8!   case 3:1 1 1 1 1 1 2 2 &gt; 8!/6!*2!   case 4:1 1 1 1 2 2 2 &gt; 7!/4!*3!   case 5:1 1 2 2 2 2 &gt; 6!/4!*2!   case 6:2 2 2 2 2 &gt; 1!   add answers of all cases =&gt; 1+9+28+35+15+1= 
<gadget id="calculator">1+9+28+35+15+1</gadget>
<output>89</output>
89   ANSWER:89
<result>B</result>
How many ways A boy can reach the top of stairs which contain 10 steps, when he can take either one or two steps every time?