Fill in the blank with the most suitable word from the options given…

The correct answer is Option (2) → lie

Complete sentence: The nurse asked the patient to lie down and take some rest for speedy recovery. The patient is to rest his own body, with no object, and "asked ... to" needs the base form, so "to lie down".

Option	Form and use	Example
(1) lain	Lain is the past participle of lie. It is used with has/have/had, not after "to".	The letter had lain unopened for a week.
(2) lie (answer)	Lie (to rest in a flat position) takes no object: lie – lay – lain.	The doctor told him to lie down for an hour after lunch.
(3) lay	Lay (to put something down) takes an object: lay – laid – laid. As the base form, lay means "put something down" and needs an object. "Lay down" with no object is a common mistake for "lie down". As the past tense of lie, it cannot follow "to".	Lay the book on the table.
(4) laid	Laid is the past tense and past participle of lay (put down). It cannot follow "to" and needs an object.	She laid the keys on the desk.