Which Task Is More Difficult for an Experienced Reader to Perform

Which task is more difficult for an experienced reader to perform than it is for someone just learning to read?

A) Look at the names of colors written in different colors and say the color of each word, rather than the word itself.
B) Look at a word flashed on the screen and identify the whole word.
C) Look at two complex pictures flashed on the screen and say whether or not they were the same.
D) Look at a series of words and identify the one that is written right to left instead of left to right.