问题如下：
A US institutional investor in search of yield decides to buy Italian government bonds for her portfolio but wants to hedge against the risk of exchange rate fluctuations. She enters a cross-currency basis swap, with the same payment dates as the bonds, where at inception she delivers US dollars in exchange for euros for use in purchasing the Italian bonds. The notional principals on the swap are most likely exchanged:
选项：
A.at inception only.
at maturity only
both at inception and at maturity.
解释：
C is correct.
In a cross- currency basis swap, the goals of the transaction are to achieve favorable funding and exchange rates and to swap the foreign currency amounts back to the currency of choice—in this case, the US dollar—at maturity. There is one exchange rate specified in the swap that is used to determine the notional principals in the two currencies, exchanged at inception and at maturity.
请问swap在期初签订的时候是怎么约定（表述）principal和期间现金流的呢？可以举个实际例子么
