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If a force given by $a \hat i + b \hat j$ acts on an object as the object is displaced by $c \hat i + d \hat j$, the work done on the object is

$ac + bd$

$ab + cd$

$\sqrt{a^{2} + b^{2}} \sqrt{c^{2} + d^{2}}$

$abcd \cdot \hat i \cdot \hat j$

$\sqrt{abcd} \cdot \hat i \cdot \hat j$