Heating a mixture of 1,3-diphenylacetone and acrolein in trimethylamine gives a product, C...

Heating a mixture of 1,3-diphenylacetone and acrolein in trimethylamine gives a product, C18H16O, in 53% yield. The mechanism for product formation is a Michael addition followed by an intramolecular aldol condensation. Which of the following is the product of this reaction?

A) A

B) B

C) C

D) D