I can't use my HTC one SV. It only shows the recovery mode, please help me. What should I do?

[AC Question]

This is the only shows up on my screen.
***LOCKED***
K2_UL PVT SHIP S-ON RL
HBOOT-2.21.0000
0S-3.12.707.2
eMMC-boot 1024MB
Dec 18 2013, 20:04:50:0

FASTBOOT USB

<VOL UP> to previous item
<VOL DOWN> to next item
<POWER> to select item

BOOTLOADER
REBOOT
REBOOT BOOTLOADER
POWER DOWN

Please help me guys. Huge thanks in advance!

 

[mbanu]

flash stock rom