This question checks who actually created the economics prize that is linked to the Nobel name.
Svenska Handelsbanken: This is a private Swedish bank, separate from the central bank, and it did not fund this prize, so it is wrong.
International Monetary Fund: The IMF is a global lending institution with no role in setting up this award, so this option does not fit.
Economics Department of Oxford University: A university department does not fund national prizes of this scale, so this is wrong too.
Sveriges Riksbank: Sweden's central bank, Sveriges Riksbank, established this prize in 1968 to mark its 300th anniversary, officially named the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel.
So option D, Sveriges Riksbank, is correct.
Let's summarize:
Unlike the other five original Nobel prizes, the economics prize was added later by Sweden's central bank, not by Alfred Nobel's will.
This is a frequently asked general knowledge fact about the Nobel prizes.