Answer: a. Two adjacent angles can be complementary
This is another way of saying two angles next to each other add to 90 degrees. In other words, two angles touching each other forming a corner.
Two adjacent angles can be supplementary, so choice B is false.
An acute angle is always adjacent to an obtuse angle, so choice C is false.
Two right angles can be adjacent, and they would form a straight (180 degree) angle, so that's why choice D is false.
