Q2 The key symbol involved in showing more than one thing happening in parallel is
a thick black bar
a diamond
a circle
a special kind of arrow

Q3 Two arrows could legally come out of the same activity:
True
False

Q4 (This one's unfair of me: you don't have the information to answer it. Try anyway!) If two arrows go into a thick black bar, and then one arrow comes from the bar into an activity A, then removing the black bar and making the original two arrows go straight into A would:
make no difference to the meaning of the diagram
make a difference to the meaning of the diagram
make the diagram illegal