Other countries' currencies are either fixed in value or <i><b>fluctuate against</b></i> the dollar in the world's foreign exchange markets.<br/><br/>This sentence is in my College English textbook. But I guess <i><u>fluctuate <b>with</b></u></i> would be a better collocation.<br/><br/>Which one do you like, <i>fluctuate against</i> or <i>fluctuate with</i>?<br/><br/>Thanks in advance!