Why Is It That Marquita Demonstrates Inattentional Blindness to Her

Why is it that Marquita demonstrates inattentional blindness to her husband when he is discussing a shopping list with her while she is checking her Facebook account for new updates?

A) We can only effectively process parallel sensory channels if they relate to the same topic, otherwise the sensory inputs can interfere with each other. If Marquita tries to do both, she will accomplish neither.
B) The human sensory systems of receptive vision and receptive hearing use the same part of the brain, so only one can be effectively used at any given moment. This is why she cannot read one thing and listen to her husband at the same time.
C) Our ability to process multiple types of sensory input is limited by our willingness to attend equally to those different stimuli. Marquita is less interested in her husband's conversation, so she misses most of what he is saying.
D) Inattentional blindness serves the evolutionary purpose of helping us attend only to threatening or noxious stimuli, so Marquita is prioritizing finding any potentially negative posts on her Facebook account.