One double bond consists 4 electrons, so 2 double bonds means 8 electrons
Answer:

Explanation:
means initial angular velocity, which is 0 rev/min
means final angular velocity, which is 
t means time t= 3.20 s
one revolution is equivalent to 2πrad so the final angular velocity is:
= (2π/60) *2.513*10^{4} rad/s
= 2628.5 rad/s
so the angular acceleration, α will be:
α = 2628.5 rad/s / 3.20 s

so the rotational motion about a fixed axis is:
+ 2αΔTita where ΔTita is the angle in radians
so now find the ΔTita the subject of the formula
ΔTita = 


Answer:
The correct statements would be
- Cyanobacteria allowed organisms that rely on oxygen to evolve.
- Cyanobacteria preceded the first photosynthetic organisms.
- Cyanobacteria produced excess oxygen.
Cyanobacteria, also termed as blue-green algae are the prokaryotes which are able to perform photosynthesis.
They were the major contributors of oxygen in the atmosphere and thus helped the organisms that rely on oxygen to evolve.
By the process of endosymbiosis, they lead to the origin of plants. The chloroplasts present in green plants is considered as the cyanobacteria living in the plant cell. It helps in photosynthesis and in return plants cell provides shelter to it.
It is believed that the oxygen released from early cyanobacteria reacted with dissolved iron ions to form iron oxide.
Vs - velocity on beginning
ve - velocity on ending. You've got:

So he needed 4 second.