Write the decimal number 39 to base 2

A.
10011 base 2 
B.
110111 base 2 
C.
111001 base 2 
D.
100101 base 2 
E.
19.5 base 2
Correct Answer: Option A
Explanation
(begin{array}{cc} 2 & 39\ 2 & 19 R 1\ 2 & 9 R 1\2 & 4 R 0\2 & 1 R 0\ 2 & 1 R 1end{array})
= 10011 base 2