2. Identify the following as human (H) or nonhuman (N) possible sources of error:

a. The balance used has not calibrated since it was originally plugged in___

b. Not putting the final answers in their correct number of significant figures___

c. Just as you were recording the temperature of a solution, the room suddenly feels cooler___

d. The electronic scale you use reads 0.05 g too high for all your mass measurements___