We present chemical abundances for four main sequence B stars in the young cluster NGC 2004 in the Large Magellanic Cloud ( LMC ) .
Apart from H ii regions , unevolved OB-type stars are currently the only accessible source of present-day CNO abundances for the MCs not altered by stellar evolution .
Using UVES on the VLT , we obtained spectra of sufficient resolution ( R = 20 000 ) and signal-to-noise ( S/N \geq 100 ) to derive abundances for a variety of elements ( He , C , N , O , Mg and Si ) with NLTE line formation . This study doubles the number of main sequence B stars in the LMC with detailed chemical abundances .
More importantly and in contrast to previous studies , we find no CNO abundance anomalies brought on by e.g .
binary interaction or rotational mixing .
Thus , this is the first time that abundances from H ii regions in the LMC can sensibly be cross-checked against those from B stars by excluding evolutionary effects .
We confirm the H ii -region CNO abundances to within the errors , in particular the extraordinarily low nitrogen abundance of \varepsilon ( N ) \simeq 7.0 .
Taken at face value , the nebular carbon abundance is 0.16 dex below the B-star value which could be interpreted in terms of interstellar dust depletion .
Oxygen abundances from the two sources agree to within 0.03 dex . In comparison with the Galactic thin disk at MC metallicities , the Magellanic Clouds are clearly nitrogen-poor environments .