Which of the following statements are correct regarding Ullman’s Theory of Spatial Interaction?

A) Complementarity refers to the mutual benefits gained through trade between locations with differing resources.

B) Transferability focuses on the distance and time taken to transport goods, irrespective of costs.

C) Intervening opportunities prevent spatial interaction by offering alternatives at a lower cost.

D) "Friction of distance" only applies to low-value, heavy goods like cement.