The weight of ${\mathrm{AgNO}}_3$ (Mol.wt = 170) present in 100 ml of its 0.25M solution is

We know that the formula of molarity can be mathematically expressed as: 

Molarity $=\frac{\text{ W eight }}{\text{ Molecular weight }}\times \frac{1000}{ \mathrm{V}\left(\mathrm{ml}\right)}$

Substituting the quantities provided in the question:
$0·25=\frac{\text{ Weight }}{170}\times \frac{1000}{100}$

weight $=17\times 0·25$

            $=4·25\mathrm{gm}$

Therefore, option A is the correct answer