Answer
Angle ABC is smaller than DEF. ABC is an acute angle while DEF is an obtuse angle.
Work Step by Step
First, look at both angles. You will see that ABC has a narrower opening than DEF, meaning it is a smaller angle (the angle ABC will measure fewer degrees than DEF).
Also, intuitively, you can see that angle ABC is narrower than the angle of a standard piece of paper (which is a right angle, also known as a 90$^{\circ}$ angle), which means it is an acute angle. DEF is wider than the angle of a piece of paper, so it is an obtuse angle.
