Which equation represents a proportional relationship?
y=2x2
y = 4x - 2
y= 1/2x +3
y=5x

D:  y = 5x

Step-by-step explanation:

According to Google, a proportional relationship is one in which two quantities vary directly with each other. We say the variable y varies directly as x if: y=kx. for some constant k , called the constant of proportionality.  So the only one in that form would be the y = kx.  

The constant k = 5

the mistake in the pattern is that :

b. the decimal point was moved one too many place values each time

the correct pattern could be made by :

b. moving the decimal point to the right the same numbers of place values as the exponents