If an object is said to be moving at 10 m/s due north. the measurement 10 m/s north would be best described as a) a speed. b) a velocity. c) neither a speed or velocity d) either a speed or a velocity.

Before answering this question,first we have to understand a vector.

A vector quantity is a physical quantity which has not only magnitude but also direction for it's complete specifications.It is also in accordance with the paraellogram law of vector addition.

As per the question the object is moving at 10 m/s due north.The magnitude of this quantity is 10 m/s.The direction of the quantity is towrds north.Hence the quantity given in the question has magnitude as well as direction.

As the quantity given here refers to the distance travelled per unit time, the quantity will be either speed or velocity.The quantity can not be considered as speed .It is because speed in a given direction is called velocity.

Hence the quantity is velocity .

The correct option is 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 =