1. S: The whole class. P: laughed loudly at the story
2. S: class P: laughed
3. S: hours P: passed
4. S: The workmen P: repaired the dam
The subject of the sentence is who or what the sentence is about. In sentence number 1 and 2, the sentence is about "The whole class". The complete subject contains the specific subject and any modifiers connected to it. "The" and "whole" are adjectives that modify class so these are part of the complete subject. However, the simple subject is the subject without modifiers, so for the simple subject you would only put "class". The predicate is the rest of the sentence. It includes the verb phrase and any extra information. The sentence for 1 and 2 has the complete predicate as "laughed loudly at the store". The verb phrase is "laughed" so this is the simple predicate.