Which sentence with a transition is punctuated correctly?

a. I trained hard for the marathon, however, I failed to finish.

b. I trained hard for the marathon however I failed to finish.

c. I trained hard for the marathon; however, I failed to finish.

d. I trained hard for the marathon; however I failed to finish.

In this excerpt from "quality" by john galsworthy, which two parts clearly indicate the literary point of view of the essay? that tenement had a certain quiet distinction; there was no sign upon its face that he made for any of the royal family—merely his own german name of gessler brothers; and in the window a few pairs of boots. i remember that it always troubled me to account for those unvarying boots in the window, for he made only what was ordered, reaching nothing down, and it seemed so inconceivable that what he made could ever have failed to fit. had he bought them to put there? that, too, seemed inconceivable. he would never have tolerated in his house leather on which he had not worked himself. besides, they were too beautiful—the pair of pumps, so inexpressibly slim, the patent leathers with cloth tops, making water come into one's mouth, the tall brown riding boots with marvellous sooty glow, as if, though new, they had been worn a hundred years. those pairs could only have been made by one who saw before him the soul of boot—so truly were they prototypes incarnating the very spirit of all foot-gear. these thoughts, of course, came to me later, though even when i was promoted to him, at the age of perhaps fourteen, some inkling haunted me of the dignity of himself and brother. for to make boots—such boots as he made—seemed to me then, and still seems to me, mysterious and wonderful.