Which sentence is a run-on sentence?

A.
The day after tomorrow, Louisa will run in a 5-mile race to raise money for charity.

B.
Some people stretch before exercising; I prefer to jog slowly.

C.
I like to run laps around the track, but Louisa enjoys running on the cross-country trails.

D.
Louisa stretches before she runs, she also stretches after she runs.
i need help on this one

Question

Which sentence is a run-on sentence?	
 
 A.
The day after tomorrow, Louisa will run in a 5-mile race to raise money for charity.
 
 B.
Some people stretch before exercising; I prefer to jog slowly.
 
 C.
I like to run laps around the track, but Louisa enjoys running on the cross-country trails.
 
 D.
Louisa stretches before she runs, she also stretches after she runs. 
i need help on this one

inowalst · Answer

Which sentence keeps going when it should have a period somewhere in the sentence?

anonymous · Answer

I think it is B

anonymous · Answer

thanks

inowalst · Answer

B isn't right because it has the ;

inowalst · Answer

If it didn't, then that would be the run-on, but its not.