Suppose a triangle has sides a, b, c, and the angle opposite the side of length "a" is obtuse. what must be true?

Angles corespond with legnth of side
angle oposite a is obtuse
osbtuse meas move than 90
all angles in a triangle add to 180
180/2=90
since that angle oposite a is bigger than half, that angle is bigger than the oterh angles
so therefor
a>b
a>c

we know that from pythagoran theorem that the square of the longest side is equal to the squares of the other 2 sides
the angle oposite that longest side is 90
obtuse>90 so it is longer legnth
a is longest side
b^2+c^2<a^2

the answer is D

Wow. that is a really cool question.