What is the past perfect form of the verb "to lay" in the sentence "Yesterday, I ___ the book down on the table. Where is it today?"

The past perfect form of the verb "to lay" is "had laid." However, in the context of the options provided, "laid" is the simple past form, which is used to indicate that the action of laying the book down occurred at a specific time in the past.

In the sentence "Yesterday, I ___ the book down on the table," the action is situated in the past, hence the correct form to complete this sentence is "laid." This indicates that the action was completed yesterday, prior to the current moment in the narrative.

The other options do not fit appropriately in this context. "Lain" is the past participle form used with "to have" or "to be," and "lay" serves as the simple past of "to lie down," which is a different verb altogether. "Laies" is not a standard form of the verb in English. Therefore, "laid" is the most fitting choice for indicating that the action occurred in the past.