Answer:
B 5 cm
Explanation:
The bottom leg of the shaded triangle is 1/2 of the length of the side, so is 3 cm. The vertical leg of the shaded triangle is the height of the pyramid, given as 4 cm.
The slant height is the hypotenuse of the shaded triangle, so can be found from your knowledge of the 3-4-5 triangle, or from the Pythagorean theorem.
If s is the slant height, then ...
s^2 = 3^2 + 4^2 = 9 +16 = 25
s = √25 = 5
The slant height is 5 cm.