If in 2015, the US dollar's exchange rate with the Sudanese pound was .38433 dollars per pound and in 2018, the exchange rate was .20068 dollars per pound, it would indicate that in the period from 2015 to 2018, the dollar

A.strengthened against the pound.

B.weakened against the pound.

C.was unrelated to the value of the pound.

D.the answer cannot be determined without knowing the number of pounds needed to buy a dollar