  A possible origin of kHz QPOs in low-mass X-ray binaries is proposed. Recent
numerical MHD simulations of accretion disks with turbulent magnetic fields of
MRI definitely show the presence of two-armed spiral structure in quasi-steady
state of accretion disks. In such deformed disks, two-armed ($m=2$) c-mode
($n=1$) oscillations are excited by wave-wave resonant instability. Among these
excited oscillations, the fundamental in the radial direction ($n_r=0$) will be
the higher kHz QPO of a twin QPOs, and the first overtone ($n_r=1$) in the
radial direction will be the lower kHz QPO of the twin. A possible cause of the
twin high-frequency QPOs (HFQPOs) in BH X-ray binaries is also discussed.
