Bài giải:

Ta có: 4AB = 3AC $\Rightarrow AB=\frac{3}{4}AC$

Ta có: $\Delta ABC,\widehat{A}={{90}^{0}}$

$\Rightarrow B{{C}^{2}}=A{{B}^{2}}+A{{C}^{2}}$ (định lí Py-ta-go)

$\Rightarrow 400=\frac{9}{16}A{{C}^{2}}+A{{C}^{2}}$

$\Rightarrow 400=\frac{9}{16}A{{C}^{2}}+A{{C}^{2}}$

$\Rightarrow \frac{25}{16}A{{C}^{2}}=400$

$\Rightarrow A{{C}^{2}}=256$

$\Rightarrow AC=16$cm

$\Rightarrow AB=12$cm

Đáp án đúng là C