When can sentence fragments actually make a piece of writing more effective

"dogs make wonderful pets because they us stay happy and healthy"the topic sentence is "dogs make wonderful pets" i need writing a sentence that is unrelated to the topic and can be eliminated.

Who was the last member of the stuart line whose death left britain without a clear successor? a. george i b. queen anne c. charles ii d. queen elizabeth

Choose the best paraphrase of bashes haiku an old silent pond a frog jumps into the pond splash silence again a.the pond was silent until the frog jumped in splashing now alternates with quiet b.a pond will never be silent after one frog jumps into it and starts splashing around c. a frog jumps into a quiet pond there is a splash then all is quiet once more d. there was once an accident body of water that a frog splashed into and died