What is the next number of the following sequence
1,2,3,5,8,13,?  Pick one: A) 25 B) 21 C) 20 D) 24 E) 28
1+2= 
<gadget id="calculator">1+2</gadget>
<output>3</output>
3   2+3= 
<gadget id="calculator">2+3</gadget>
<output>5</output>
5   3+5= 
<gadget id="calculator">3+5</gadget>
<output>8</output>
8   5+8= 
<gadget id="calculator">5+8</gadget>
<output>13</output>
13   8+13= 
<gadget id="calculator">8+13</gadget>
<output>21</output>
21   therefore next no. is 21   ANSWER:21
<result>B</result>
What is the next number of the following sequence
1,2,3,5,8,13,?