Which of the following expressions, when evaluated, equals an irrational number?

don't just give the answer, i already know what it is, i need a good explanation so that i understand the problem and can answers ones after it.

sqrt2
a.)
sqrt8

sqrt8
b.)
sqrt2

c.) (sqrt8)^2

d.) sqrt2 * sqrt8

e.) sqrt2 + sqrt8

Agroup of student volunteers participates in a study designed to assess several behavioral interventions for improving output in a repetitive task. prior to the beginning of the study, all volunteers unknowingly observed, and their output is measured. at the beginning of the study, prior to any intervention, the volunteers perform the same task under the observation of a study administrator, and their overall output increases. which of the following terms describes this phenomenon? a. simpson's paradox b. hawthorne effect are d. novelty effect d. pygmalion effect e. observer-expectancy effect