An Experiment Requires Participants to Quickly Determine If a Target

An experiment requires participants to quickly determine if a target is present.Which of the following tasks is likely to produce the longest reaction time?

A) Identifying a small red circle in a field of medium and large red circles.
B) Identifying a red vertical line in a field of small red circles and blue horizontal lines.
C) Identifying a blue vertical line in a field of red vertical lines.
D) Identifying a red vertical line in a field of red horizontal and blue vertical lines.