Last Year, Rebecca Left Her Residuary Estate (Worth £1million) to Tony

Last year, Rebecca left her residuary estate (worth £1million) to Tony and Teresa on trust to be divided between her grandchildren in such shares as David might by deed appoint.
Which of the following statements (there may be more than one) are true?

A) David is under no obligation to make a decision about the division of the estate.
B) If one of the grandchildren is dead, David could choose that grandchild's surviving spouse as a beneficiary instead.
C) In the absence of a decision by David, the fund would probably be divided in equal shares between all of the children and grandchildren in equal shares.
D) David cannot appoint himself as a beneficiary (unless he is one of Rebecca's grandchildren) , but he can agree with one of the grandchildren to appoint her in return for a share of what she receives.