Having decided to rent a flat, we ________ contacting all the accommodation agencies in the city .
A.set about
B.set down
C.set out
D.set up
A
set about+(doing)sth意为“开始为……忙碌”。set down意为“放下……,写下”。set out意为“出发”。set out+to do意为“着手……”。set up意为“搭(帐篷),建立,设立”。