Which index should Marvin use as a benchmark when evaluating the performance of his mutual fund?

Index $1$

Index $2$

Index $3$

Index $4$

Beta

$0\mathrm{.}56$

$0\mathrm{.}96$

$1\mathrm{.}56$

$0\mathrm{.}75$

r$-$squared

$0\mathrm{.}65$

$0\mathrm{.}83$

$0\mathrm{.}74$

$0\mathrm{.}98$

a$.$

Index $1.$

b$.$

Index $2.$

c$.$

Index $3.$

d$.$

Index $4.$