B - FRONTS occur when two AIR MASSES meet!
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 to your question is fish
Photosynthesis has a role in the cycling of matter and flow of energy into and out of organisms. The flow of energy and cycling of matter can be traced. The chemical reaction by which plants produce complex food molecules (sugars) requires an energy input (i.e., from sunlight) to occur hope this helps :)