Help please, i’ll give brainlest! it’s out of a dice with 6 sides,

i’m doing probability. if you do answer can someone simply explain to me what complement means. i’ve learned about it but it’s confusing for me. thanks <3

P(complement of 4)
Α. 1/6
B. 5/6
C. 2/6
D. 4/6

Adolphin is swimming with her friend. the dolphin jumps to a height of 4.54.54, point, 5 meters above the surface of the water as her friend swims 9.89.89, point, 8 meters directly below her. what is the position of the dolphin's friend relative to the surface of the water? meters