Which is a run-on sentence?

a.
she sews her own clothes; she looks very stylish.

b.
he tried to make a call, but he couldn't get service.

c.
she moved to town three months ago, she is pretty shy.

d.
he tied the boat to the dock, so it wouldn't float away.

I think its A because reading I thought that it looked grammatically wrong B has correct punctuation so does C so I think that it's A don't hate me too much if i'm wrong

Explanation:

no its not a run on sentence however i think you meant wet suits not sours also a run on sentence would be like surfers surf all winter long in southern california by using wet sours to keep them warm and the live their all year long