一标称值50mm的量块经校准后，确定其长度实际值Z为49. 999926mm,且合成标准不确定度为u(l) =36. 4nm。则正确的测量结果报告方式有（ ）。[2008年真题]
Al - 49. 999926mm ± 36. 4nm
Bl =49. 999926mm, U(I) = 73nm(k = 2)
Cl = (49. 99993 ±0. 00008)mm(k =2)
Dl=49. 999926mm, U(l) = 8 x 10-5 mm (k =2)
El =49. 999926mm，u( l) =36. 4nm