Mrs Lim completed a puzzle at $$5.45$$ p.m.  She took $$\rm 3h15min$$ to complete it.  At what time did she start working on the puzzle? 
选项为:A:$$2.30$$ p.m.  B:$$3.00$$ p.m.  C:$$3.30$$ p.m.  D:$$9.00$$ p.m.  请回答其中一个选项.