1a. Leontief's paradox refers to the results of an empirical study that

A.supported the Ricardian model

B.contradicted the Ricardian model

C.supported the Heckscher-Ohlin model

D.contradicted the Heckscher-Ohlin model

1b. The main purpose of the gravity model is to explain

a.the volume of trade

b.the pattern of trade

c.why not all countries benefit from trade

d.the existence of intra-industry trade