Figure (a) shows a spring P extends by 5 cm when it is hung with a 0.5 kg weight. Figure (b) shows four springs P are arranged in a system and it is
hung with a 1.0 kg load.

What is the total extension of the spring system?

A 5.0cm
B 10.0 cm
С 15.0 cm
D 20.0 cm
E 25.0 cm

Noted: the figure （a）and （b）on the picture above

Thanks for giving answer to me.​

i guess it’s a and b

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =

the right answer is 0.3 meters per second