Referring to the Law of 'Rebuttable Presumptions' Which of the Following

Referring to the law of 'rebuttable presumptions' which of the following is correct?

A) Evidence that a child born within 5 months of marriage raises a rebuttable presumption that the child was conceived before marriage, it will be for the party seeking to assert that the child was conceived before marriage to adduce evidence that the child born was a full-term baby (i.e. was not born prematurely) to rebut the presumption raised.
B) Evidence that a marriage was celebrated will raise a rebuttable presumption that the parties are married, the husband seeks to show that there was no valid marriage; he will need to adduce evidence to rebut the presumption that the parties were married.
C) When there is no word from a person for more than 7 years and reasonable enquiries have been made to establish the person's existence, there will be a presumption that the person is dead; the wife seeking to establish that her husband is dead will need to adduce evidence that establishes beyond doubt that her husband is dead.
D) Evidence that a surgeon is a known expert in a field will raise a rebuttable presumption that the surgeon carried out a specific operation in his field of expertise correctly and it will be for the claimant to prove otherwise.