ETFs. What is an ETF? How do ETFs differ from open$-$end stock funds?

$($Select the best answer below.$)$

A$.$ ETFs are similar to closed$-$end mutual funds except they can be traded like stocks throughout the day. ETFs are designed to mimic particular stock indexes or sectors and are actively managed. Open$-$end stock funds only trade after the markets close and are traded at net asset value.

B$.$ ETFs are similar to open$-$end mutual funds except they can be traded like stocks throughout the day. ETFs are designed to mimic particular stock indexes or sectors and are not actively managed. Closed$-$end stock funds only trade after the markets close and are traded at net asset value.

C$.$ ETFs are similar to closed$-$end mutual funds except they can be traded like stocks throughout the day. ETFs are designed to mimic particular stock indexes or sectors and are not actively managed. Open$-$end stock funds only trade after the markets close and are traded at net asset value.

D$.$ ETFs are similar to closed$-$end mutual funds except they cannot be traded like stocks throughout the day. ETFs are designed to mimic particular stock indexes or sectors and are not actively managed. Open$-$end stock funds only trade during the day and are traded at net asset value.