The diagram shown is a UML Sequence Diagram, which is used to depict the interaction and order of messages between objects.
In the given diagram, we can see two occurrences of the message 'm' with different parameters (100 and 200), and one occurrence of the message 'p' with the parameter "run".
To determine the minimum number of occurrences that must happen before the reception of 'm(200)', we look at the order of messages:
* The message 'm(100)' must occur.
* The message 'p("run")' must occur after 'm(100)' and before 'm(200)'.
These two occurrences are the minimum necessary before 'm(200)' can be received by the object. The dashed line represents a return message, which does not count as an occurrence for this purpose.
Therefore, the correct answer is:
B; 2