How is the number 378,412 correctly read in word form?

Three hundred seventy-eight thousand, four hundred twelve

Three hundred seventy-eight million, four hundred twelve

Thirty-seven thousand, eight hundred forty-twelve

Three hundred seventy-eight, four hundred twelve

In the number $5,284,910$, what does the comma between the $5$ and the $2$ separate?

The millions period from the thousands period

The thousands period from the ones period

The hundred thousands place from the ten thousands place

The thousands place from the hundreds place

Six million, nine thousand, twenty

Six million, nine hundred thousand, twenty

Six million, nine thousand, two

Sixty million, nine thousand, twenty