This is a physics question, not biology, but...
f=1/T where f is frequency and T is the period.
f= 1/(1/3)=3
frequency =3 Hz
It's A, a limiting factor is something that constrains the population size
I’m sorry what are you asking for ml!?
The answer, my dear, is D. Because if you divide each side by 3, 36 equals to 12 and 39 equals to 13. I hope this helps!