1. The option a. 10 mL has the most uncertainty associated with it, because it has only 2 significative figures, while 10.0 mL has three significant figures and 10.00 has four significant figures.
2. The volume of solution that remains is 145.675 mL - 24.2 mL = 121.475 mL rounded to one decimal = 121.5 mL, given that the measure with the most uncerntainty has only one decimal.
