Here , the density of the material is 4g cm³ but it is not given in CGS system.
$\sf{As\:we\:know\:that:}$
$\sf\bold{Density=}$ $\sf\dfrac{Mass}{Volume}$
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$\sf\small{Density\:of\:the\:material=4}$ $\sf\dfrac{g}{cm^2}$
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$\sf{It\:is\:given\:that:}$
In the system of units the mass is 100gram.
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Hence,
$\sf{The\:mass\:unit\:for\:4g=}$ $\sf\dfrac{4}{100}$ $\sf{units}$
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In the system of units,the length is 10cm.
Henceforth,
$\sf\small{The\:length \:for\:1cm\:units=}$ $\sf\dfrac{1}{10}$ $\sf{units}$
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<u>☆</u><u> </u><u>Substitute</u><u> </u><u>the</u><u> </u><u>required</u><u> </u><u>values</u><u> </u><u>in</u><u> </u><u>the</u><u> </u><u>given</u><u> </u><u>formula</u><u>-</u>
$\sf\purple{Density=}$ $\sf\dfrac\purple{Mass}\purple{volume}$
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$\sf\underline\bold{Density\:of\:the\:material:}$
= $\sf\dfrac{4/100}{1/10^3}$ $\sf\bold{units}$
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= $\sf\dfrac{4/100}{1/1000}$ $\sf\bold{units}$
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= $\sf\dfrac{4000}{100}$ $\sf\bold{units}$
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$\sf\underline\bold\blue{=40\:units}$
$\sf\small{Therefore,option\:2nd\:is\:correct!}$
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