Answer:
I am not really sure but i think its option 2
Explanation:
When air is blown into the open pipe,
L = 
where nis any integral number 1,2,3,4 etc. and λ is the wavelength of the oscillation
⇒λ=
Note here that n=1 is for fundamental, n=2 is first harmonic and so on..
⇒ third harmonic will be n=4
Given L=6m, n=4, solving for λ we get:
λ=
=3m
Relationship of frequency(f), velocity of sound (c) and wavelength(λ) is:
c=f.λ Or f= 
⇒f=
≈115 Hz
Answer:
The first source of energy in a food chain is producer.
Explanation: In the food chain, the producer will be a plant that a primary consumer, a herbivore eats. The herbivore gets eaten by a secondary consumer, carnivorous. When the carnivore dies, it becomes energy for a decomposer.