Which of the following methods of expressing concentration are unitless?

Select the INCORRECT statement/s from the following:

(a) 22 books have infinite significant figures

(b) In the answer of calculation $2.5 \times 1.25$ has four significant figures,.

(c) Zero's preceding to first non-zero digit are significant

(d) In the answer of calculation $12.11+18.0+1.012$ has three significant figures

0.48 g of an organic compound on complete combustion produced 0.22 g of $\mathrm{CO}_2$. The percentage of C in the given organic compound is

An aqueous solution of alcohol contains $$18 \mathrm{~g}$$ of water and $$414 \mathrm{~g}$$ of ethyl alcohol. The mole fraction of water is