Help please i have to finish soon

Which statement justifies why angle ebc measures 90?

The four students in the table below each recorded the time and distance traveled while exercising. exercising distance (miles) time (minutes) gia 2 30 harris 5 50 ian 3 40 jackson 4 80 which list ranks the students from fastest walker to slowest walker? jackson, gia, ian, harris harris, jackson, ian, gia harris, ian, gia, jackson jackson, harris, ian, gia

How many and of which kind of roots does the equation f(x)=x3−x2−x+1