The magnetic field due to the loop always opposes the external magnetic field.(b) The flux due to the loop always has the opposite sign as the flux due to the external magnetic field.(c) The flux due to the loop always opposes the change in the flux due to the external magnetic field

C

Explanation:

The flux due to the loop always opposes the change in the flux due to the external magnetic field. This occurs as a result of the current that is induced in a coil (due to a magnetic flux change through the coil) which will always be in such that it opposes the change that caused it. ... Any induced current in a coil will result in a magnetic flux that is opposite to the original changing flux. This was what  Faraday was explaining in the law of Induction

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 =