Which is the correct way to punctuate the sentence?
® Dr. Burke wanted to trust her assistant with the secret
formula; but she was afraid her assistant was a spy.
Dr. Burke wanted to trust her assistant, with the
secret formula: but she was afraid her assistant was a
spy.
• Dr. Burke wanted to trust her assistant with the secret
formula but, she was afraid her assistant was a spy.
C Dr. Burke wanted to trust her assistant with the secret
formula, but she was afraid her assistant was a spy.
