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Mydogislacey
D and E. An acute angle is any angle that is less than 90(a right angle). A is an obtuse angle(more than 90). And B + C are right angles. Hope this helps you!
an acute angle is an angle that is less than 90*. so, assuming that they are talking about a normal sheet of paper and a normal window, both are out. 

Knives pointed end is right.
Scissors as wide as they can go will be an obtuse angle so no.
A sharpened tip of a pencil will be correct.