Failing to see visible objects when our attention is directed elsewhere is called the cocktail party effect. parallel processing. inattentional blindness. blindsight.

In-attentional blindness.

Explanation:

In-attentional blindness phenomenon was coined by Arien Mack and Irvin Rock. It is a process of failure to the fully visible but visual perception of unexpected objects. Mack and Rock's earlier work explored the similar failure of awareness under the situation of selective attention. Logically, whatever we want to see can perceive through our eyes but in reality, attention plays a vital role in visual perception.  

Inability to perceive the object, this sighted blindness, it seemed to be the reason that subjects were not attending the stimulus but instead of attending another stimulus. This is called in-attentional sight blindness.

the answer is b: a lockout