Choose the correctly punctuated sentence below:
a.
We are finished learning about punctuation marks, obviously we are moving on to a writing unit.
b.
We are finished learning about punctuation marks; obviously, we are moving on to a writing unit.
c.
We are finished learning about punctuation marks obviously, we are moving on to a writing unit.
d.
We are finished learning about punctuation marks obviously we are moving, on to a writing unit.