Which is the best revision of the sentence below?
she tried to hold the dog back but anna was just not strong enough for the bulk, power and movement of the dog.

a anna tried to hold the dog back but she just was not strong enough for the bulk, power, and movement of the dog.

b. she tried to hold back the dog; but anna just was not strong enough for the bulk, power, and movement of the dog.

c. anna tried to hold back the dog, but she just was not strong enough for the bulk, power, and movement of the dog.

d. she tried to hold back the dog, but anna just was not strong enough for the bulk, power, and movement of the dog.