Please help me now!!

An energy drink company claims that its product increases students' memory levels. to support its claims, the company issues advertisements claiming that 8 out of 10 people (chosen randomly from across the country) who tried their product reported improved memory. the missing component in this study is a .

∆red ≅ ∆ by rule will give brainiest if possible

Can someone me with these two circle theorem questions asap?