The short strangle

A short strangle's upper breakeven is found by:

• Subtracting the credit from the short call strike
• Adding the total credit to the short call strike
• Adding the call's own premium only to the short call strike

Which change helps a short strangle that is still open, with the stock between the strikes?

• Implied volatility falling
• Implied volatility rising
• The stock moving sharply toward one strike