Which structure best bacteria to move through an environment?
cell membrane
flagella
ribosomes
endoplasmic reticulum

The one that best fits the description would be the FLAGELLA or flagellum (singular). The flagella is a part of cell that resembles like a whip that allow movement of the cell. Generally, the purpose of flagella is for locomotion, but its physical structure might differ depending on the organism.

The answer would be d. most contraceptives are effective when used properly