Which sentence is punctuated correctly?
A.
The mansion had a marble, fountain where water gurgled, all day long.
B.
Maurice saw a huge, splendid mansion as he rowed down the stream.
C.
The mansion was so grand, that Maurice could not take his eyes off it.
D.
Maurice thought, the people in the mansion led highly, luxurious lives.
C.
The mansion was so grand, that Maurice could not take his eyes off it.