Explain how and when to stretch ?

Explanation:

The best time to stretch is after exercise, when your muscles are warm. True and false: It's safer to stretch a warm muscle, and warm muscles are more relaxed and have greater range of motion. However, walking briskly or jogging for five minutes, until you break a light sweat, is a sufficient warm-up for stretching.

I hope it's helpful!!

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.

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 =