Final answer:
Christine acknowledges Rhoda's skill at lying by calling her an 'adroit liar', which indicates that Rhoda is indeed a good liar.
Step-by-step explanation:
Christine, in the dialogue, acknowledges that Rhoda is an adroit liar. This implies that Christine sees Rhoda as someone who is very skilled at lying, and thus option a) 'She is a good liar' is the correct answer to what Christine acknowledges about Rhoda in the dialogue. The rest of the options are not supported by the statement Christine makes about Rhoda.