orby

Millions of people travel about the country by rail， by bus，orby automobile，ordrive to and from their places of work and their homes。

三个并列的by， by， by作为travel的方式状语。

Accounts receivable go up proportionally as sales go up, whetherthe increase in dollar sales is produced by more physical volume orby inflation.

应收帐款随销额成比。而以美元计的销额是由销量通货膨胀引起。