Verified Answer :

The - article adj
Bill - SN
Must be paid - verb phrase
By - preposition
Whoever purchased the lumber - noun clause obj of the preposition

Answer: Explanation:

The sentence "The bill must be paid by whoever purchased the lumber" is written in the Passive Voice, in which the subject receives the action of the verb.

Subject: The bill

Predicate nominative/noun: paid  (after linking verb)

Direct Object of Verb: the lumber  (verb purchased)

Object of Preposition: whoever  (preposition by)