A police officer parked at the curb turns on his lights and siren, waits for traffic to clear, then pulls out and heads down the street. For an observer down the street, which is true? A. The frequency of the siren is higher and the wavelength is shorter than it was at first.
B. The wavelength of the siren is shorter than it was at first, but the frequency is the same.
C. The wavelength of the siren is shorter and the frequency is lower than it was at first.
D. The frequency of the siren is higher than it was at first, but the wavelength is the same.

the five characteristics of adolescence are biological growth and development, and undefined status, increased decision making, increased pressure and the search of self.

i need with 1.3.2 investigate cycling o2 and co2 apex

we need to see it

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 =