One cause of the outbreak of World War I was caused by

a the break out o the Russian revolution
b rising tensions among European powers
c the killing of Serbian national
d the invasion by Germany of Belgium

yes ur right it is B

A
C
B

my anser is b

IT IS

A
C
B

rising tensions am...

a
c
b

I agree -- but there's another answer that is more specific.

Is it c?

C is the best answer. It was the immediate cause of the outbreak of World War I.