what does the appendix do

什么时候用does，什么时候用do？一般现在时用do和does,比如always,usually,often、every day（year）。第一人称、第二人称和名词复数用do（I、you、we、they、cats、dogs、~s等）。 … The sports injury treatment service operates on a paying basis, as does the nutritional service.

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