A "digital word" is defined as a four-letter combination of the digits 1 and 0 only. How many "digital words" are there?
Choose the correct option:
A) 2  B) 4  C) 6  D) 8  E) 16
only digits allowed are 1 and 0 so for a 4 digit number the possibilities are   1111-&gt; 4!/4! -&gt;1   0000-&gt; 4!/3! -&gt;1   1000-&gt; 4!/3! -&gt;4   1100-&gt;4!/2!2! -&gt;6   1110-&gt;4!/3! -&gt;4   Total 1+1+4+6+4= 
<gadget id="calculator">1+1+4+6+4</gadget>
<output>16</output>
16 is possible..   16 is the answer
<result>E</result>
A "digital word" is defined as a four-letter combination of the digits 1 and 0 only. How many "digital words" are there?