Which of the following are acute angles?

Angle I is definitely an acute angle:

As for angle II, it is also an acute angle. This is because this angle is somewhere in between 0^{°} and 90^{°}.

Angle III is not an acute angle as it is greater than 90^{°}.

Again, angle IV is not an acute angle as this angle is greater than 90^{°}.

Clearly, only I and II are acute angles. Hence, the answer is B.

Feeling bored of worksheets? Try Zap Zap Math game to find out the secret of people who fall in love with math.