18.What kind of angle is formed by a corner of a square table?
A. Right
B. obtuse C. acute D. straight
19.What kind of angle is shown by an opened book whose measure is greater than 90°?
A. Right
B. obtuse
C. acute D. straight
20.What kind of angle is illustrated when the hands of a clock form 1:20
A. Right
B. obtuse C. acute D. straight​