please tell me which is the correct answer

The Sharpe ratio is defined as the risk premium divided by the variance of the portfolio.

For the capital allocation line, the higher the borrowing rate, the higher is the slope.

The capital allocation line depicts the relationship between portfolio expected returns and variances.

If investors can borrow and lend with the same risk free rate, the relationship between return and risk is linear for a portfolio of one risky asset and one risk free asset.