Directions: This passage contains errors and an omission. Choose the correct option to correct the corresponding error and complete the passage. I have noticed that ‘No Parking’ boards are appearing on all gates of our (9) neighbourhood. They are also been pinned on all the tree trunks around here. (10) On close inspection, I saw that they are actually advertisement boards. (11) I am aghast as it seemed to have escaped the notice of everyone. (12)

Which word(s) correctly replace(s) ‘am’ in line (12)?