According to the graph, which of the following statements is CORRECT?

a$.$ Indifference curve $1$ represents lower level of utility than indifference curve $4.$

b$.$ Portfolio D is a better choice than Portfolio $C$ due to its higher expected return.

c$.$ Portfolio $P$ is the optimal choice to this investor as it provides the highest expected retur

d$.$ Portfolio $C$ is a better choice than Portfolio $D$ due to its higher utility.

e$.$ None of the above option is correct.