How do we know if our data is heteroskedastic?

a) We can examine the residual plot and will always see a clear pattern if thereis heteroskedasticity

b) We can use an F-test to determine if there is heteroskedasticity

c) We cannot know for sure; it is an assumption that we will make out of caution

d) A large difference betiveen the R2 and the adjusted-R2 will indicate the presence of heteroskedasticity