His cheekbones were high and wide, and strong deep lines cut down his cheeks, in curves beside his mouth. His hands were hard, with broad fingers
and nails as thick and ridged as little clamshells. The space between thumb and forefinger and the palms of his hands were shiny with calluses.
Which technique is the author using to reveal the character?

Describing actions
Describing physical traits
Describing emotions
Describing thoughts