【C7】A．variationB．varietyC．exchangeD．shift

【C8】A．numberB．varietyC．sumD．series

【28】A．variationB．balanceC．frequencyD．stability

【29】A．displayingB．describingC．creatingD．exchanging

A．To lower their exchange rates.B．To regulate their exchange rates.C．To raise their re

【C18】A．varianceB．varietyC．variationD．variable

A．variationB．varietyC．varianceD．variable