Answer: D. Ecosystem
Explanation: The ducks are interacting with trees and algae with are all part of an ecosystem.

Work done = 100J
Distance = 5 meters
Force = ?

Force = 100/5 = 20N
Therefore, the force needed is 20 Newtons
The correct answer is option d, that is, neurotransmitters.
A neurotransmitter refers to a chemical component, which is discharged at the terminal of a nerve fiber by the introduction of a nerve impulse, and by diffusing across the junction or synapse. It helps in the transfer of the impulse to another muscle fiber, nerve fiber, or some other composition. Acetylcholine is a kind of neurotransmitter, that is, used by neurons in the CNS and the PNS in the control of activities ranging from heart rate and muscle contraction to digestion and memory.
The right answer is have a frank, open discussion with him about his feelings.
The combination of a depressive disorder with a serious physical illness such as cancer can make the identification and treatment of depression more difficult. Indeed, the symptoms of depression may be underestimated and attributed to the other disease.