Serving static images in Express

Which of these code snippets can you use to do this?

You want to serve static images in two different directories named thisd and thatd.

a. app.use(express.static('thisd'))
   app.use(express.static('thatd'))

b. app.use(express.static('thisd',"thatd"))

c. app.use('static', express.static('thisd'))
   app.use('static', express.static('thatd'))

d. app.use('static', express.static('thisd',"thatd"))