The answer of the question is A
Answer:
The feeding relationships among the species in a community determine the community's trophic structure. C)
The mass of a star can be determined by studying D) binary star systems.
Although there may be other ways to determine the mass of a star, this is the most common one which is widely used all over the world when it comes to measuring objects in the universe.
9) Richter scale
10)Seismograph
11) measurement of the amplitude of the largest wave
I do believe to are correct