As a measure of money flow, the balance of payments differs from the balance of trade primarily because of its greater

A．tying the value of world currencies to the value of gold.
B．greater centralized control of world trade.
C．substituting several different monetary standards for a single unified standard.
D．increasingly stable currencies.

A．it does not establish a generally accepted international medium of exchange.
B．it establishes no relationship between the value of a given currency and the value of gold.
C．the relationship it established between the value of any currency and the value of gold is indirect rather than direct.
D．it is a two-tiered rather than a single-tiered system.