Is it Mother has been lying in bed all morning?

The correct sentence is: "Mother has been lying in bed all morning."

In this sentence, "Mother" is the subject and "has been lying in bed all morning" is the verb phrase. "Has been lying" is the present perfect continuous tense of the verb "lie", which is used to describe an action that started in the past and is still continuing in the present. "All morning" is a time phrase that indicates the duration of the action.

The sentence "Is it Mother has been lying in bed all morning?" is incorrect because it uses the interrogative form of the verb "to be" ("is") instead of the present perfect continuous tense of the verb "lie" ("has been lying").