A valve is a flap of tissue that prevents blood from flowing back
Answer:
I think the answer is b am sorry if it is wrong
Explanation:
Your answer is A
Pls mark me brainiest and I sure hope this helps you
when the two waves interfere with eachother to make a dark spot the periodic difference of the two waves is π . the wave length for 2π is 600nm
. ie. for π difference it is 300nm
