Over the past decade, the U$.$S$.$ equity has had an increasing inflow from equity ETFs while having consistent outflows from actively managed equity funds. Which of the following might have caused this change of capital flow?

a$.$ ETF charges management fees as low as $0\mathrm{.}07\%$ of the amount of money invested while mutual funds charge $1\mathrm{.}4\%$ on average.

b$.$ Investors can obtain full transparency on all holdings in the ETFs as well as in mutual funds.

c$.$ Investors can short$-$sell ETFs as well as mutual funds.

d$.$ All of these