Answer:
Reciprocal altruism is one of the altruism behaviors in which an individual organism helps in increasing the fitness of another organism by reducing the fitness of itself temporarily in expectation of the same behavior from another organism in the future later.
It takes place in the same set of organism partners which is a continuous interaction ion in stable groups of organisms.
Thus, the correct answer would be - an ongoing interaction in the same set of partners.
Anaphase 1 is the correct answer
A Muscle Contraction Is Triggered When an Action Potential Travels Along the Nerves to the Muscles. Muscle contraction begins when the nervous system generates a signal. The signal, an impulse called an action potential, travels through a type of nerve cell called a motor neuron.