Right choice is (a) 18
To explain I would say: The OV7670 Camera Module has 18 pins which includes the Vdd for Power supply, GND for grounding, SDIOC for SCCB clock, SDIOD for SCCB data, VSYNC for Vertical Sync, HREF for Horizontal Sync, PCLK for Pixel Clock, XCLK for System Clock, D0 to D7 pins are for Video output, RESET for resetting the module, and PDWN for powering down the module.