Two measures x and y were taken on 18 subjects. The first of two regressions, Regression I, yielded y=24.5+16.1x and had the following residual plot. The second regression, Regression II, yielded log(y)=1.6+0.51log(x) and had the following residual plot.

a) Both regressions are linear
b) Regression II is logarithmic
c) Regression I is exponential
d) Neither regression is appropriate