Look at this series: 1,4,9,16,... What number should come next?
Choose the most appropriate option:  A) 18  B) 27  C) 30  D) 25  E) 24
Explanation: This is a series of perfect square numbers.   1*1= 
<gadget id="calculator">1*1</gadget>
<output>1</output>
1   2*2= 
<gadget id="calculator">2*2</gadget>
<output>4</output>
4   3*3= 
<gadget id="calculator">3*3</gadget>
<output>9</output>
9   4*4= 
<gadget id="calculator">4*4</gadget>
<output>16</output>
16   5*5= 
<gadget id="calculator">5*5</gadget>
<output>25</output>
25 and so on.   Answer: Option 25
<result>D</result>
Look at this series: 1,4,9,16,... What number should come next?