Answer:
The high school band gave a concert, and it lasted for an hour.
Explanation:
In the sentence above, the "high school band" is the subject of the sentence. The verb or action in the sentence is "gave" and the object is "concert." "It lasted for an hour" is another independent clause so you need the conjunction "and" with a comma before it. You could also use a semi-colon without the conjunction. Also, note that the verb in both clauses is in the past simple tense. You could also say "The high school band gave a concert that lasted for an hour."
