\(1g=1000mg\to1mg=0.001g\\\\1min=60s\to1s=\frac{1}{60}min\\\\5.8\times10^6\ mg/s=5.8\times10^6\times\frac{0.001}{\frac{1}{60}}\ g/min\\\\=5.8\times10^6\times0.001\times60\ g/min=(5.8\times60)\times(10^6\times0.001)\ g/min\\\\=348\times10^3\ g/min=\boxed{3.48\times10^5\ g/min}\\\\Answer:\boxed{C}\)
