A flea and dog are an example of Choose...
, because the flea irritates the dog’s skin and feeds on its blood. Certain bacteria live in the digestive tract of humans, and their relationship is an example of
Choose...
because the bacteria help humans to break down the food they eat. Cattle egrets eat insects off the back of an elephant, which is an example of
Choose...
because the cattle egrets benefit without either harming or helping the elephants.