Which of the following statements about sequence diagrams is wrong?
a. this is a request from the object sending the message to the object receiving the message. the request is for the receiver to carry out one of its (the receiver’s) operations. usually, this entails the sender waiting for the receiver to carry out that operation. because the sender waits for the receiver (that is, "synchs up" with the receiver), this
message is also referred to as synchronous..
b. uml signifies the synchronous message type with a filled
arrowhead at the end of a solid line.
c. another kind of message is asynchronous. with this one,
the sender transfers control to the receiver and doesn’t wait
for the operation to complete.
d. the symbol for the return message is an openstick
arrowhead with a solid line.