A fundamental distinction between trend projection and linear regression is that:

A fundamental distinction between trend projection and linear regression is that:
 
  A) trend projection uses least squares while linear regression does not.
  B) only linear regression can have a negative slope.
  C) in trend projection the independent variable is time; in linear regression the independent variable need not be time, but can be any variable with explanatory power.
  D) trend projection can be a function of several variables, while linear regression can only be a function of one variable.
  E) trend projection uses two smoothing constants, not just one.