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.
Telephase in pretty sure that's how you spell it
Answer:
C, recycle, but if I could choose two it would be reuse.
Reasoning:
Reusing things and recycling things are both useful for the community.