Label the parts of the trumpet creeper flower. I am particularly interested in A and C, as I believe A is the calyx but my professor informed me that...

Label the parts of the trumpet creeper flower. I am particularly interested in A and C, as I believe A is the calyx but my professor informed me that a calyx is often green. I am thinking A might be the receptacle or the ovary but I am not 100% certain. Thanks!!