在$-2$，$\sqrt{4}$，$\sqrt{2}$，$3.14$， $\sqrt[3]{-27}$，$\frac{\mathrm{\pi }}{5}$，这$6$个数中，无理数共有(        )

(____) Ottawa is the capital city of Canada.

(____) The CN Tower is very tall.

(____) It has five yellow stars.

(____) They speak English and French.

(____) I live in China.

如图，Rt△ABC中，∠ACB=90°，点D为斜边AB的中点，CD=6cm，则AB的长为____ cm．