Tom says:
I saw a dog I had never seen before running about in the street on its own.
Pete replies:
a. Maybe one of your neighbors bought a new dog that escaped.
b. One of your neighbors might have bought a new dog that escaped.
c. One of your neighbors might have bought a new dog and it escaped.
d. One of your neighbors might have bought a new dog and it might have escaped.
Which of the above sentences are grammatically correct and acceptable in this context?