The correct answer is From different social and ethnic backgrounds.
Explanation:
The purpose of science studies is to gain an understanding of specific phenomena and use this in the benefit of the world or humanity. Moreover, science is guided by objective methods and these are applied all around the world. This feature allows scientists from all kinds of social and ethnic backgrounds to study the same phenomena and obtain similar results, which is essential for the progress of scientific knowledge. This is exemplified by two different labs in two different countries studying drug absorption because the results of these two studies can be analyzed together to understand drug absorption.
In this context, one factor that contributes to the progress of scientific knowledge is the effort of scientists "from different social and ethnic backgrounds".
Scientists should control most possible variables in experiments to get the most valid and correct data. If many variables are included in experiments it is more difficult to interpret what is causing a different outcome.
Answer:
Value of
for the given redox reaction is 
Explanation:
Redox reaction with states of species:

Reaction quotient for this redox reaction:
![Q_{p}=\frac{[Cr^{3+}]^{2}.P_{Cl_{2}}^{3}}{[H^{+}]^{14}.[Cr_{2}O_{7}^{2-}].[Cl^{-}]^{6}}](https://tex.z-dn.net/?f=Q_%7Bp%7D%3D%5Cfrac%7B%5BCr%5E%7B3%2B%7D%5D%5E%7B2%7D.P_%7BCl_%7B2%7D%7D%5E%7B3%7D%7D%7B%5BH%5E%7B%2B%7D%5D%5E%7B14%7D.%5BCr_%7B2%7DO_%7B7%7D%5E%7B2-%7D%5D.%5BCl%5E%7B-%7D%5D%5E%7B6%7D%7D)
Species inside third braket represent concentration in molarity, P represent pressure in atm and concentration of
is taken as 1 due to the fact that
is a pure liquid.
![pH=-log[H^{+}]](https://tex.z-dn.net/?f=pH%3D-log%5BH%5E%7B%2B%7D%5D)
So, ![[H^{+}]=10^{-pH}](https://tex.z-dn.net/?f=%5BH%5E%7B%2B%7D%5D%3D10%5E%7B-pH%7D)
Plug in all the given values in the equation of
:

A solution is turning blue means, it is turning it's behavior to Basic from Acidic. Reagent D must be a Basic component so it is increasing the pH of the solution. As reaction does not depend on the phase of the component, it could be anything i.e., Solid, Liquid or gas.
Hope this helps!
This is a combustion reaction.
2C6H6 + 9O2➡️ 6CO2 + 6H2O