Answer
Option $(a)$
Work Step by Step
RECALL:
In the equation $y=mx+b$, $m$=slope and $b$ is the y-coordinate of the y-intercept. The y-intercept point is $(0, b)$.
The given equation, $y=\frac{2}{3}x+\frac{3}{4}$, has $b=\frac{3}{4}$, so its y-intercept is $(0, \frac{3}{4})$.
Thus, the answer is Option $(a)$.