Short- Term Movements of Finance Around the World Can Be

Short- term movements of finance around the world can be controlled in a variety of ways. Which of the following has not been suggested as one of them?

A) Limits on the proportion of assets that can be traded in any one day/week/whenever
B) A Tobin tax of, say, 0.5% per transaction
C) Having to deposit part of a transaction in the central bank of the recipient country
D) Delays in processing transactions to make speculation more risky