这道题怎么理解，解释一下

问题如下：

Margin transactions are facilitated and computed in which process?

选项：

A.

clearing

B.

settlement

C.

execution

D.

collateralization

解释：

Clearing is the process of recording counterparties’ identities and calculating margin and payment obligations. Settlement is the process of facilitating payment and transferring money when the contract is closed out. Execution is the initial step of entering into a derivatives contract. Collateralization is the process of posting assets as security to minimize credit risk