If a country has a current account surplus, the capital account is zero and the official reserves do not change, then

a.

there has to be a capital inflow higher than the current account surplus.

b.

there has to be a capital outflow of the same volume as the current account surplus.

c.

there has to be a capital inflow of the same volume as the current account surplus.

d.

there has to be a capital inflow less than the current account surplus.