Is there a way to determine whether or not a reagents is still acceptable?

Facial shaving brushes are either bulb-shaped or fan-shaped. an experiment is to be conducted to determine whether the lather thickness is the same for both types of shaving brushes. in previous studies, it was determined that shaving brush size (small, medium, large) is associated with lather thickness, but shaving brush type (wolf whiskers, maggard razors, frank shaving, and so on) is not associated with lather thickness. how could the experiment best be conducted? by blocking on shaving brush size by blocking on shaving brush type by blocking on shaving brush shape by blocking on lather thickness without blocking

Which of the following is not true about hydroelectricity a. use of gravitational force of flowing water b. its the most widely used renewable energy c. it has a high output of co2 that fossil fuels d. it has no direct waste asap

Afootball game between the thunder and the sharks is in its closing minutes, with the thunder ahead by 20 points. the thunder’s coach considers sending in the second-string quarterback. this would reduce the risk of the star quarterback getting injured, but the second-string quarterback is not very good. complete the passage describing the coach’s decision in economic terms.