Joshua was grounded for coming home late. He wasn't allowed to watch television.

Which is the best way to combine these two sentences?
A.
Joshua was grounded for coming home late wasn't allowed to watch television.
B.
Joshua was grounded for coming home late he wasn't allowed to watch television.
C.
Because Joshua was grounded for coming home late wasn't allowed to watch television.
D.
Joshua was grounded for coming home late, so he wasn't allowed to watch television.

D. Joshua was grounded for coming home late, so he wasn't allowed to watch television.