Answer
$(d)$
Work Step by Step
(a) is true (c cancels on the LHS)
(b) is true (b is the LCD)
(c) is true, (bd is the LCD)
(d) is not true, because
$\displaystyle \frac{\frac{a}{b}}{\frac{c}{d}}=\frac{a}{b}\div\frac{c}{d}=\frac{a}{b}\times\frac{d}{c}=\frac{ad}{bc}$
