Answer:
C. cell- tissue- organ- organ- system
Explanation:
Percentage w/v means that weight of solute present in 100 ml of a solution. Hence, 15% w/v means that 15 gram of solute per 100 ml of solution.
Hence, for 2 L (or 2000 mL) preparation the amount of mass will be calculated as follows.

= 300 g
Thus, we can conclude that weight of Tris-HCL required is 300 g.
The answer is b) DNA to RNA to proteins
It could be xenon, enon is a chemical element with the symbol Xe and atomic number 54. It is a colorless, dense, odorless noble gas found in Earth's atmosphere in trace amounts.[11] Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized.[12][13][14]