Answer:
message flows are modeled with solid arrows
Explanation:
In Business Process Model and Notation (BPMN), message flows are used in the collaboration diagram to show how two or more distinct processes within the model, communicate and collaborate with each other without any form of central control.
Dash lines together with an empty circle are used for the message flow to show where the message comes from and an empty arrow head is used to show where the message would be terminating in the model.