How is a hedge ratio commonly determined?

Question $27$ options:

$1)$

By discounting the optimal number of futures to sell per $$1$ of cash position using the yield involved.

$2)$

By using the ratio of the most recent spot and futures price changes.

$3)$

By running an ordinary least squares regression of changes in spot prices on changes in futures prices.

$4)$

By using the hedging factor.

$5)$

By squaring the correlation between past changes in spot asset prices and futures prices.