Answer
$negative$, $III$, $60^\circ$, $-\frac{\sqrt 3}{2}$.
Work Step by Step
We can identify $\theta=240^\circ$ to be in quadrant $III$, thus $sin\theta$ will be $negative$. The reference angle is the acute angle formed by its terminal line with x-axis and it can be found as $240^\circ-180^\circ=60^\circ$, thus the exact value is $sin240^\circ=-sin60^\circ=-\frac{\sqrt 3}{2}$.
The answers are $negative$, $III$, $60^\circ$, $-\frac{\sqrt 3}{2}$.
