Which of the following relationships is symbiotic?

A group of ants work together to build an underground nest.

A tick latches on to the body of a dog and feeds on the dog's blood.

Abee pollinates a flower while feeding on the flower's nectar.

A remora attaches to the body of a shark and feeds on scraps when the shark eats.

Two male red-winged blackbirds fight over territory.

A male bluebird and a female bluebird provide care for their offspring.