Answer :

To determine which equation has a constant of proportionality equal to 4, we can evaluate each equation by finding the ratio of the coefficients of [tex]\(x\)[/tex] and [tex]\(y\)[/tex]. Let's go through each option one by one.

### Option A: [tex]\(4y = 4x\)[/tex]
To find the constant of proportionality:
1. Divide both sides by [tex]\(4\)[/tex]:
[tex]\[ y = x \][/tex]
So the constant of proportionality is:
[tex]\[ \frac{x}{y} = 1 \][/tex]

### Option B: [tex]\(4y = 12x\)[/tex]
To find the constant of proportionality:
1. Divide both sides by [tex]\(4\)[/tex]:
[tex]\[ y = 3x \][/tex]
So the constant of proportionality is:
[tex]\[ \frac{x}{y} = 3 \][/tex]

### Option C: [tex]\(3y = 4x\)[/tex]
To find the constant of proportionality:
1. Divide both sides by [tex]\(3\)[/tex]:
[tex]\[ y = \frac{4}{3}x \][/tex]
So the constant of proportionality is:
[tex]\[ \frac{x}{y} = \frac{4}{3} \approx 1.33 \][/tex]

### Option D: [tex]\(3y = 12x\)[/tex]
To find the constant of proportionality:
1. Divide both sides by [tex]\(3\)[/tex]:
[tex]\[ y = 4x \][/tex]
So the constant of proportionality is:
[tex]\[ \frac{x}{y} = 4 \][/tex]

### Conclusion:
From the calculations, we see that the constant of proportionality equal to 4 corresponds to option D: [tex]\(3y = 12x\)[/tex]. Therefore, the equation with a constant of proportionality equal to 4 is:

D. [tex]\(3y = 12x\)[/tex]