Arriva has raced into the lead to lead the FTSE 250 after the rail and bus group said it had received an approach about a possible offer. Shares in the company climbed yesterday amid rumours of a possible 700p-a-share bid from German transport operator Deutsche Bahn.Singaporean firm ComfortDelGro, the operator of the London bus company Metroline, has also been mentioned as a possible bidder.Arriva's rivals FirstGroup, National Express and Stagecoach are higher in sympathy.Hikma Pharmaceuticals is a little off colour after it reported a 33% increase in 2009 operating profit and said it was confident of continuing growth.Shares in Military decoy specialist Chemring are under attack even after it reported a 5% increase in trade during the four months to the end of February at constant currency despite taking a hit from snow storms in both the UK and US.FTSE 250 - RisersArriva (ARI) 682.00p +17.69%FirstGroup (FGP) 389.10p +5.56%CSR (CSR) 489.00p +5.32%National Express Group (NEX) 228.00p +4.40%Aquarius Platinum Ltd. (AQP) 405.80p +3.86%Gem Diamonds (GEMD) 241.50p +3.51%DSG International (DSGI) 35.14p +3.32%888 Holdings (888) 112.20p +3.22%Stagecoach Group (SGC) 186.80p +3.09%Cookson Group (CKSN) 537.00p +3.07%FTSE 250 - FallersJD Wetherspoon (JDW) 491.10p -5.38%Computacenter (CCC) 300.00p -3.88%Amlin (AML) 407.40p -3.85%Hikma Pharmaceuticals (HIK) 574.00p -3.53%Interserve (IRV) 203.30p -3.47%Ecofin Water & Power Opportunities (ECWO) 142.00p -3.40%Robert Wiseman (RWD) 492.00p -2.19%BTG (BGC) 179.60p -2.13%Chemring Group (CHG) 3,336.00p -1.74%SIG (SHI) 126.90p -1.63%.00p -1.74%SIG (SHI) 126.90p -1.63%