Of the following, which has the largest odd factor? 
Overseas Competition->Knowledge Point->Number Theory Modules->Factors and Multiples->Basic Concepts of Factors and Multiples
Keep dividing each by $$2$$ until you get an odd number.  $$\text{A}$$.$$2\times15$$.  $$\text{B}$$.$$2\times2\times 2 \times 2\times2\times1$$.  $$\text{C}$$.$$2\times2\times9$$.  $$\text{D}$$.$$2\times2 \times 2\times5$$. 