#### Answer

(a)

#### Work Step by Step

Since the sum of the interior angles of a triangle is $180$, then in a right triangle any other angle $\theta$ should satisfy
$$0\lt\theta\lt \pi/2$$
so the right answer is (a).

Published by
W. H. Freeman

ISBN 10:
1464125260

ISBN 13:
978-1-46412-526-3

(a)

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