Final answer:
The relationship where the start of one activity triggers the start of another activity is called causation or cause and effect.
Step-by-step explanation:
The relationship where the start of one activity triggers the start of another activity is called causation or cause and effect. For example, if you press a button on your computer, it triggers the start of a program. In this case, the action of pressing the button is the cause and the start of the program is the effect. Understanding causation is important in many fields of study, such as history, where events are often analyzed in terms of their causes and effects.