(6) In the summer, school started at 6 a.m. (7) School did not end until 5 p.m. Which is the most effective way to combine sentences (6) and (7)?
The summer school day, ending at 5 p.m., started at 6 a.m.

In the summer, school started at 6 a.m. and did not end until 5 p.m.

Starting at 6 a.m. and not ending until 5 p.m. was school in the summer.

Not ending until 5 p.m., school in the summer started at 6 a.m.