Suppose you are interested in how subjects perform under different temperature conditions. Subjects work in one of three rooms. The rooms differ only with respect to temperature. You instruct all subjects to solve the same jigsaw puzzle. You then measure how long it takes each subject to finish. In the research described above, differences in temperature conditions serves as which of the following:
observation
internal attribute
independent variable
dependent variable

Achemistry student needs to standardize a fresh solution of sodium hydroxide. he carefully weighs out of oxalic acid , a diprotic acid that can be purchased inexpensively in high purity, and dissolves it in of distilled water. the student then titrates the oxalic acid solution with his sodium hydroxide solution. when the titration reaches the equivalence point, the student finds he has used of sodium hydroxide solution.calculate the molarity of the student's sodium hydroxide solution. be sure your answer has the correct number of significant digits.