Which of the following are obtuse angles?

Angle I is definitely an obtuse angle.

As for angle II, it is not an obtuse angle. This is because this angle is less than 90°.

Angle III is not an obtuse angle as it is greater than 180°.

Angle IV is an obtuse angle as this angle is more than 90° and less than 180°.

Clearly, only I and IV are obtuse angles. Hence, the answer is B.

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