Given a text T, and several options, according to the question posed in the text T to choose the most appropriate option from the options as the answer, please directly output the most appropriate option, do not need to output the explanation.

With respect to return-generating models, which of the following statements is most accurate? Return-generating models are used to directly estimate the:
Option A:expected return of a security.
Option B:weights of securities in a portfolio.
Option C:parameters of the capital market line.

Answer: A