Keep dividing each by $$2$$ until you get an odd number.  $$\text{A}$$.$$2\times15$$.  $$\text{B}$$.$$2\times2\times 2 \times 2\times2\times1$$.  $$\text{C}$$.$$2\times2\times9$$.  $$\text{D}$$.$$2\times2 \times 2\times5$$. 
Of the following, which has the largest odd factor? 
a) $$30$$ 
b) $$32$$ 
c) $$36$$ 
d) $$40$$ 