C) La chica es trabajadora
'trabajadoro' is a masculine way of worker so d is incorrect
b says 'las chicas' which means the girls, not one girl so that is incorrect
'el' is a masculine way to refer to a male so a is incorrect
hope it helped! I know the 'masculine' and 'feminine' thing can get confusing so if you have any other questions, dont hesitate to ask!
