The equation 3y + 4z = 0 represents a

plane containing z-axis plane containing x-axis plane containing y-axis line with direction number 0, 3, 4

plane containing x-axis

The equation 3y + 4z = 0 or 0x + 3y + 4z = 0 represents a plane passing through the origin and contains the line $\frac{x}{1}=\frac{y}{0}=\frac{z}{0}$ i.e. x-axis.